Hi there, and thank you both for your replies.

I appreciate it!
About anxiety, I deffinately did have that problem back when the depression was at it's worst. That's what would keep me up all night, I would just have a million thoughts and worries running through my head all night, so I couldn't sleep. Last night was much the same. It was 5am before I fell asleep. That's the third night in a row. But for the most part lately I'm so tired it's EASY to fall asleep.
And yes, I am on an anti-depressant now (Celexa/Cipramil), but even before that I was tired a lot. Don't teens need a lot more sleep anyway? I just don't know if this is normal...?
No I'm not overweight or any of those other things.
What exactly does a sleep study involve...?
As for the sleep apnea, as far as I know it's not in my family. But then, I don't really know any of my family except for my imediate family on account of them living on the other side of the world and all.

One thing though is that my mum is frequently up half the night, or she wakes up and finds it difficult to get back to sleep. That's the problem I used to have too, it started about the same time for both of us.
Well thanks again for your replies.
Ashlee