I have the same exact problem Giga. Fall asleep at 11, wake up at 2 or 3. Won't be able to sleep til' like 5 or 6. Which isn't very practical as I have lectures at 9, so most of the time I sleep through lectures. But the days I do manage to attend I'm useless as ****.

I tried sleeping tablets, the ones I had didn't do much. It would send me asleep quicker but I would still physically wake up in the middle of the morning. I read a good way to get asleep and shit is to make your bed look inviting. Get some new covers, extra pillows, another blanket, whatever catches the Z's. Pretty much the same thing Donut said, association.