Sleep is very important, especailly when you are young. 7-10 hours is great, but everyone is different (i get about 4 or 5 ) if you wake up on the weekends, around the same time you do during the week, then you know you are getting enough sleep.
When I read your email, you sounded so much like me at your age. I worried about everything,, are you like that too? I think a lot of my stomach problems are from being like that. In fact, I know that is the probelm. We can make ourself sick. Trust me, if you can limit the junk food, limit the pop, you dont have to never have it, just dont live off it. Get some excercise, dont smoke, drink water and eat some fiber, you are doing all you can do. If you worry a lot about stuff, just know that everyone does, everyone feels just like you do. Haveing a positive attitude also helps. Remember there is only one you, make sure you tell yourself everyday that you are great. No one feels bad when they are happy. Let me know how you are.