What over-the-counter supplements would help me sleep?

Have you been referred to a sleep specialist? I have heard of people with extreme insomnia "re-training" their sleeping patterns by staying in their room between 11pm and 6am and sleeping (if possible) then staying out of their rooms any other time. Another thing you could do is think about your sleeping environment. I know it sounds silly, but maybe re-arranging the furniture in your room, or re-painting or redecorating it as you may have formed a negative association unconsciously with your surroundings. Do you find it easier sleeping in other places? I don't think sedatives would help you long term as it doesn't sound like a simple problem that can be treated with short-term solutions. I don't think any over the counter things would help either, in the UK you can only get sedating antihistamines which are only supposed to be for short term use anyway. You can buy some herbal things which contain ingredients such as Valerian which you could have a try, but make sure you have a chat with your doctor or pharmacist first to check they are suitable. But it really sounds like you need specialist help, especially as you've had the problem for so long and from such a young age. Hope this helps