I Don't Know What's Wrong...

All my life i've had trouble sleeping. It started the day my mom brought me home from the hospital, apparently. I only found this out within the past two years (i'm 19). Most babies wake up every few hours. I'd sleep all night and my mom couldn't wake me during the day.
As far back as I can remember i've had trouble getting to sleep at night and waking up in the morning. But it's really really bad now. Well, this week actually it's being pretty good but that's part of the problem: there's no consistancy. For the past week i've actually been getting to bed early and getting up early, all refreshed adn everything. Then last night I felt like I was waking up every twenty minutes, being awake for about ten seconds and then falling back asleep.
I consider myself semi-nocturnal because of any given day the easiest time for me to fall asleep is between 6-9am. I don't know why. And since that's when the world wants me to wake up....
I am pretty sure my circadian clock is messed up because even if i'm "on a schedule" it will mess up for no apparent reason.
But the most recent development is that I can't wake up. My alarm clock will go off and off and off and I won't wake up and I drive everyone on my hall crazy (i live in a dorm).
However, I bought a new alarm clock like three weeks ago and it's waking me up pretty well but I think it's because my body hasn't gotten used to it.
I have actually slept through a tornado, I sleep like the dead.
I definately have experienced rem sleep in the first few minutes of sleep. I will doze off and get woken up in just ten minutes and have had a vivid dream with a plot and everything.
I also can't fall asleep if someone else in the room is there or if I know someone will enter. When I was in high school and shared a room with my older sister it drove her nuts because she'd stay up late to study and to be nice she'd go and do it in the living room.. So at 2 am when she came back into the room she'd be like "why are you still up?" and i'd be like "i couldn't sleep because I knew you were coming back".
The not being able to wake up thing is the thing that really scares me now, and I know it's affecting my sleep because i'm scared to go to sleep because I know I have no control over getting awake.
You may wonder why i've not gone to a doctor yet but there are reasons: one) money. Two) I know I wouldn't sleep at a sleep clinic because of all the people that if I didn't see I would still know were there and c) I tried melatonin (sp?) a few years ago and just that supplement made me sleep 18 hours straight and so i'm terrified of being put on some drug by a doctor without knowing what the results would be.
Especially since I am in school and I don't want to experiment with stuff. It's bad enough i'm sleeping through classes now: drugs could be worse. They coudl be better, I know, but it's that whole "the monster you know is better than the monster you don't" thing.
Ok, well I figured i'd see what people think I may have (after all if I have researched it before I go to a doctor it means i'm better informed and that's good)