Im having trouble sleeping at night?

It is summer and I get to bed around 10 at night, but I usually fall asleep around 3 in the morning or earlier... Then to keep my sleep pattern I have to wake up at around 9 a.m, every night it is a struggle for me to get some sleep... I've tried exercise before bed, stretching, drinking a glass of water, milk, ect. But all of these don't work... Whenever I feel tired, I want to fall asleep but my body wakes up as soon as I try... All I want to do while trying to sleep is to do something else... My mind wanders and eventually I find something interesting and I want to do it... Anyway, that's basically whyni can't get any sleep... On odd occasions I get a well rest 7-8 hours but most of the times I only get 3 or 4 hours of sleep... I'm 15 and I'm fit, so phisically I'm fine but while I'm trying to sleep I can't get comfortable and I want to move live crazy... This doesn't only happen during summer it happens every year, even during school weeks... Please help me... this lack of sleep is depriving me physically and mentally...