How old are you? I know that teenagers in general just have later sleep patterns, and therefore rarely get enough sleep that they need.
I know that when my AS oldest son was a teenager, we tried Melatonin for a while. I don't think it helped him, but it has been known to help others. Also, I have "heard" that a smell like lilac or lavendar will help to relax people. Aromatherapy, possibly, could help.
I've been having trouble sleeping, off and on, lately, and I've been wondering if I'm over-stimulated by television and/or the computer. I was thinking of going back to the routine that we used to try with our children when they were little -- turning down the lights, reading a book before bed, doing something less stimulating just before you go to bed so that your brain gets a chance to swtich gears and slow down.