i can see insomnia has had an effect on your spelling.
anyway, serious now. not sleeping is very bad for your health. i wouldn't resort to drugs as agreed to by most others. i think you shouldn't be too anxious at night about not being able to sleep or what time it is, how long you've been awake etc. it gets you pumped up and nervous, making sleep all the more difficult. just relax, regardless of the time, set an alarm the next morning and get up as planned, use up some energy in daily activities (do not fall asleep in class), that makes sleep easier. do not take a nap after school because you're tired, do your hmk, study, and sleep at night.
Honestly, i'm getting less and less sleep as the HSC is approaching (since yr 7). I think it's affected my memory to some degree, but i try to get at least 8-8.5 hours. somedays 6 is all i can manage, but i make up for that on weekends. it might also be possible that there is a certain 'root of evil' e.g HSC stress, work at the root of the problem would be cool in this case. And plus, insomnia is a cycle, so get out of it asap.