When I can't sleep, I find that just doing some deep breathing and relaxation techniques helps....The kind of breathing/freeing your mind/de-stress/sort of thing that you will find practiced in Yoga classes... For the most part, if i can't sleep, it's because my head's racing with all sorts of different thoughts, so when you free yourself of those, and focus on breathing, it does help.
Since you are actually getting enough sleep, I wouldn't recommend any sort of medication, as sometimes people can react badly, and I don't think a doctor would prescribe them if there's no real need for it.