Catherine Benfield wasn't diagnosed with OCD until she was was 31, after she had her first child, though it would appear she's had it all her life. She recovered with the help of therapy - and by creating a character who personifies her obsessive-compulsive behaviour.
"She's got the big ears, because she's like a startled hare, she's listening out.
"She's bedraggled, because she's been through a lot and she's normally having some kind of panic.
"The big eyes are about making sure she's keeping an eye out for danger.
"The big legs - for running," like a frightened hare, says Catherine Benfield.
And she can change too - very quickly. She can be quiet one moment, but then her mood will swing and she'll suddenly be feeling at the end of her tether, forlorn, broken and, at her worst, absolutely beaten.
You have now met Olivia.
She is a visualisation - a character created by Catherine to personify the condition she has lived with since she was a child.
The O in Olivia stands for OCD, an abbreviation for obsessive-compulsive disorder.
People are often mistaken about OCD, Catherine says. So many people think it's about being very fastidious and organising your pens very precisely on your desk but it's actually a serious anxiety-related mental health condition, involving intrusive obsessive thoughts, images and fears.
In an effort to prevent one of her fears coming true, Catherine would feel compelled to carry out a repetitive physical or mental act - in technical terms the fear is the "obsession" and the repetitive act is the "compulsion". This would provide temporary relief from the anxiety, but then it might return, compelling her to repeat the behaviour again and again.
Catherine says OCD often preys on kind and caring people.
"They're compassionate, they're sensitive to the needs of others," she says. "They love the people around them to an intensity where they will do anything to stop harm coming to them."
Between the ages of four and five, Catherine would stand staring out of the window for long periods, waiting for family members to return home and fearing that they had come to harm.
"I thought somehow the silent vigil would help bring them home safely," she says.
As a teenager she was terrified to be the last one to leave the house, because of the fear that it would burn down once she had gone - she would compulsively check the cooker was switched off and switches unplugged. And to ensure everyone was safe she would compulsively lock all doors and windows, and remove all trip hazards.
These routines could take hours to perform, and if one thing disturbed the process she would start all over again.
As time went on she became so busy with her studies and her job as a teacher that OCD had less of an impact on her life. It wasn't until she had her baby son at the age of 31 that she became really unwell.
"I had a horrible labour. I came away, I was very weak and I just couldn't do very much physically, it gave me a lot of time to think," she says.
"Almost immediately I started staying up all night to check he was breathing. Every parent has been known to check their child's breathing, particularly when it's newborn, but it grew to the point where I didn't feel like I could leave him at all. I wasn't sleeping, I wasn't eating."
At first she was terrified that something or someone would hurt him. Then she began to worry that she might harm him herself.
"I remember sitting on the sofa looking at my mother-in-law holding my kid in front of a wall and thinking how easy it would be to get up and throw him against it," she says.
"I could see it all, it was absolutely horrible and really detailed, very vivid, accompanied with images in my head of my future and what I'd have done to my family and my friends as a result."
She didn't know it, but what she was experiencing was perinatal OCD. Women with this condition would never actually carry out the actions they visualise, but Catherine's intrusive thoughts left her feeling anxious, depressed and isolated.
"I didn't know it was OCD," she says. "I thought I wanted to do it. I thought, 'What kind of mother has thoughts like that about their child?'"
Consultant psychiatrist Dr Lynne Drummond says life events, both good and bad, are often a trigger for OCD.
"Childbirth is quite a major life event," she says. "Let alone the whole issue of suddenly having somebody who is completely and utterly dependent on you. Plus your [changing] hormones, plus you're knackered and you're probably at times down in the dumps and your body has had a huge change. You're physically at a lower ebb. Emotionally you have to come to grips with your change in role."
Catherine began to avoid anything that could hurt her son. She threw away all the knives in the house as she imagined herself hurting him with them. She was terrified to go on a station platform with the pram after having intrusive thoughts about pushing her son under a train.
She eventually became so anxious that she couldn't leave the house with her son.
"I was never suicidal, but I do remember at one point thinking, if the very worst comes to the very worst and I can't get through this, that is an option for me," she says.
"If you believe that you're a danger to your child, you'll do whatever you can to remove that danger and that was, I suppose, the ultimate thing that I could do."
She says no-one - including medical professionals - recognised her symptoms.
"I literally got to the point where my husband said, 'You need to come to the doctor's right now,' and so we went," says Catherine. "I walked in and I was literally like, 'I'm worried I'm going to harm my son,' and just burst into tears."
The GP told her it was anxiety and gave her medication. But when she tried to come off it her condition deteriorated again. One day, in desperation, she typed into Google "OCD and fear of harming son" and dozens of stories popped up.
"I hadn't thought that was going to happen," she says. "I thought I was a monster, and immediately everything that I had been thinking and feeling and going through was written down in front of me by all these other people."
Catherine had finally got a diagnosis - from the internet - after battling with OCD all her life. She then sought medical help, and about 18 months after she had her son Catherine started therapy.
This included cognitive behavioural therapy (CBT), a talking therapy which focuses on how your thoughts and attitudes affect your behaviour and feelings, and exposure and response prevention therapy (ERP), a form of CBT treatment where you are asked to confront your obsessions or fears and resist carrying out the compulsive behaviour.
Dr Lynne Drummond on "graded exposure" ERP therapy
What I'd do is get the patient to create a hierarchy of situations. I use a zero-to-eight scale with zero being no anxiety and eight complete panic. I'd get them to rate how anxious they would feel doing each thing without "putting things right" - in other words, performing the compulsion. I'd start with something that had an anxiety rating of three or four - mild-to-moderate anxiety - and encourage them to expose themselves to their fears for one to two hours without "putting things right". They would find that the anxiety would remain high and it would be absolutely horrible, but actually over that time it would go down - and each time they do it will be just that little bit easier.
This helped enormously, but Catherine found there was a big stumbling block on her road to recovery.
"Unless I could get a handle on the fact that actually I wasn't this monster, I wasn't going to be able to carry on getting better," she says. "And that's where Olivia came in."
Olivia was a way for Catherine to separate herself from her condition. Olivia personified her obsessions and her compulsive behaviour - but she could feel compassion for Olivia, and this enabled her to feel compassion for herself.
"If I had a really horrible thought about harming someone, I would imagine that it was Olivia hopping up and down and she was the one who was frightened, she was the one who was scared - and I'd feel for her.
"I'd be like, 'Come on don't be daft, this is just anxiety,' and by doing that I could then talk to myself in that way."
It was while she was washing up one day that the idea of Olivia came to her. She instantly visualised what Olivia looked like and decided to write a blog. Then she told her artist husband, Pete, who drew the otherworldly creature his wife described.
The impact was immediate. Catherine even went out and bought a set of knives for the house again.
Where to get help
"When I was getting the intrusive thought about the knives I could imagine Olivia bouncing up and down in a rage beside me and all I wanted to do was go, 'Look don't be silly, this is nothing, it's nothing.'"
Olivia Bamber from the charity OCD Action says therapy is the recommended treatment for OCD and that medication can also be helpful. But so can "separating OCD from yourself" - as Catherine has.
Catherine says she knows some people with OCD have called their condition "the bully", but she didn't want Olivia to be like this.
"I couldn't bear the thought of trying to imagine myself living with this evil face hovering over my shoulder. So I decided to have a character that I could show love and compassion," she says.
At the same time, Catherine worked hard on tasks set by her therapist.
She had become too terrified to go into a department store because of intrusive thoughts about throwing her son from the escalator. As part of her ERP therapy she was asked to start facing her worst fears and to travel up and down the escalators carrying her then two-year-old son in her arms.
"It was something that absolutely terrified me at first, but I went up and down those escalators so many times and on so many different occasions that I don't even think about it any more," she says.
She also had to stand on a station platform and deliberately bring on the thought of pushing her son under the train until it got to the point where she faced no anxiety at all.
"I don't see recovery as never having a symptom," she says. "I see recovery as being able to manage them or them not interfering massively in my day-to-day life."
Occasionally, Catherine says, OCD does try and nudge its way back into her life.
"As I was walking out of [my son's] bedroom last night, having said goodnight, there was a book on the floor and I thought if he gets up in the night and runs in to me he could trip on that and fall and hit his head, and so I moved it, that is what mums do, it makes sense," says Catherine.
"I got back into bed and I was like, 'Ah did I move it far enough out the way?' I knew I did, but I had to go back and I had to move it and then I was like, 'Stop it, stop it!' And that's where I employed all the stuff I learnt through using Olivia."
She didn't go back to check a second time, proving how far she has come.
But will Olivia ever disappear from her life?
"I still use that visualisation sometimes and I still use the things that I learnt from that every single day, even in areas of my life that are nothing to do with OCD," she says. "If I start having a negative thought about something - 'Did I do that right or wrong?' - I remember that self-compassion, and it started with her, so I don't think I will ever say goodbye to her."
Through her blog, Taming Olivia, Catherine now tries to help new mothers recognise the symptoms of OCD, and encourages them to show compassion towards themselves.
"It's our job to recognise our Olivias," she says, "but not to give into them."
All illustrations of Olivia by Pete Benfield
Dr Lynne Drummond is the author of Obsessive Compulsive Disorder: All You Want to Know about OCD