Why can't I sleep through the night?

For the past month or so, I haven't been able to sleep.
I usually try to fall asleep around 10 or 11, I'll just lay there until around 1. I'll finally pass out but then I'll wake up at 3,4, and 5. Then go back to bed and wake up at 7 for work.

This awful schedule is driving me crazy. I've even tried OTC sleeping pills and that doesn't seem to help either.