At first, my mother put my long lie-ins down to teenage laziness. It was only when I became unable to stay awake during lessons, at dinner, in front of the TV and in the car that she became concerned.

While sleep deprivation can send you mad, having too much also plays tricks on your brain. As I was falling asleep, I'd see figures standing over my bed, feel hands touching me, hear music and voices. These hallucinations were vivid and terrifying.

The summer I turned 14, things got even stranger. If I laughed or cried, got nervous or experienced any kind of adrenaline rush, my legs would start to shake. Soon I could barely hold a conversation without losing control of my muscles; I couldn't focus my eyes, speak or hold my head up. Every few minutes I'd collapse.

I went for MRI scans and visited countless specialists who all made the same diagnosis: narcolepsy and cataplexy, a kind of sister illness. The realisation that there was no operation to correct my symptoms was hard to swallow. I was a teenager - I just wanted to be "normal". I certainly wasn't prepared for the prospect of being on medication for the rest of my life, or to relinquish my ambition to be an actress.

I was put on a course of Ritalin and clomipramine. The hallucinations stopped and I felt less sleepy, but I certainly wasn't cured. Getting through school was a struggle. For a narcoleptic, being made to sit still and not speak while being lectured to in a warm classroom is torture.

The cataplexy also overshadowed my school years. While friends were really cool and understanding about it - making a huge joke out of who could make me laugh until I fell down - it was nerve-racking meeting new people, and I was unable to play sports or take part in the drama productions I'd enjoyed so much. This inactivity meant that I went from a size 10 to a size 16 in two years.

My gap year gave me my first taste of how hard it would be to hold down a job. Working in a museum was almost impossible - too quiet. A job in a call centre was better because I'd work in intensive three-hour bursts, the constant talking keeping me awake.

University was liberating by comparison. Here everyone napped during the day. Sleeping before lectures meant I could generally keep my eyes open and if I did nod off, there'd be plenty of other students snoring away beside me.

A few years ago my family became friends with a cranial osteopath who told me my atlas bone was in the wrong place - had I ever had an accident or problems with my head? I hadn't, but my mother did mention I had been born very fast and my head had been slightly misshapen for weeks after. His theory was that when I reached puberty, dramatic growth spurts pushed my atlas bone even further out of position, where it now hindered the flow of blood and nerves to my brain.

Over the next few weeks he tried to manipulate the bone back into the right place through a series of violent massages. The difference was gradual, but unmistakable. I am now able to live a relatively normal life; I'm still unable to drive, I'll never be a brain surgeon or operate heavy machinery, but I get by.

I continue to feel drowsy, irrespective of how much sleep I've had the night before. In fact, my sleep at night is often very disturbed as my body clock seems barely able to differentiate between day and night. I haven't slept more than four hours straight in nearly 10 years.

It's hard to maintain a social life. Days out are difficult. I will have to go home halfway through, or find somewhere else to grab a nap: toilets, park benches, pretty much anywhere. If the weather's bad, I'll jump on a bus and sleep through the route.

Sometimes I feel angry and frustrated that I can never be the person I could have been. In another way, I know I am lucky to have such severe symptoms: those with mild narcolepsy and cataplexy can go their whole lives being labelled lazy, forgetful, clumsy or stupid.

It's hard to explain the difference between my condition and ordinary tiredness but scientists have estimated that the intensity of exhaustion a narcoleptic feels can best be compared to how most people would feel if they missed three consecutive nights' sleep. It is almost painful, and eventually impossible, to keep your eyes open.

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