Go Sharks!
I bet on them in Vegas once and I wasn't sure if they were the soccer team or the hockey team. The guy taking the bet made a face and said, 'Why the hell are you putting money down if you don't even know what sport this is?' and I replied, 'They're from my hometown!" and then he totally got it.
People are actually no truly nocturnal. Your mind may want to be up, but your body does not. It sounds like your body is trying to adjust to nocturnal schedule. Plus...you'e young.
Seriously though, brains and bodies continue to develop until teh early/mid 20s, and doubly so if you are a guy.
And even when I tried to get BACK to a normal schedule where I COULD sleep in if I wanted to I would just lie awake for hours.
Is the room you sleep in completey dark? Light makes a big difference.
Sometimes, after you've stayed awake past the point your bod wants to crash, the pendulum swings the other way and you cannot sleep.
One way to help is to do trick your body's pendulum again. Next time you can't sleep, do an activity you HATE that puts you to sleep (aka bores you) or make yourself get out of bed and walk around until you feel tired. It should help.
*edit* I know I made a lot of type-os in this post, but that's what happens at 4:00 am when the keyboard is perched at a weird angle.