Alright adding in my two cents from my own experiences, textbooks, being a psych major, and that I especially wanna be an adolescent psychologist and give my friends psychological advice and get yelled at for it when it's unwanted, so sorry if I start to sound all therapisty when I respond but I tend to do stuff like this a lot, take out of my advice whatever you want.
The first thing you have to do is to not be mad at yourself for worrying. Sure it's easy to say just don't worry but from my own experience I know it is very difficult to simply turn your mind off. Regardless of anything else, you should feel a bit more happier and at ease realizing that it is perfectly okay for you to worry and that at this time it's pretty normal(though normal doesn't really exist..) and there's really no need to start analyzing whether the worrying is appopriate for your age...I started thinking too much which lead me to depressing thoughts about time moving too quickly when I was 8!
Someone gave great advice in essentially saying doing stuff about things is better than worrying. This is essentially reflection vs. rumination, or good worrying vs. bad worrying. In reflection, we worry about...perhaps weight, and when we feel we're too heavy, we start losing weight, so it is good to worry because we do something so we don't have to worry anymore. However, if we started worrying about height, worrying about how short we were, that would be rumination--worrying with no purpose because there really isn't much you can do about. Especially since you seem to have different things you worry about, if you think there's one you may be able to do something about or do things to help you not worry, perhaps you can start focusing on that worry more than the others.
The sleep thing obviously is bad, since I find the less sleep I get, the more agitated/paranoid/worried I become, so if you're getting less sleep because you're worrying, that'll make you worry more, and then you'll get less sleep, etc. Again, night was my big worry time too. The best thing I can suggest is trying to control your mind most when you go to sleep. There are different things you can try. If you have something that you love so much that it can completely overtake you or clear your mind, such as perhaps your violin or a particular broadway CD...whenever I play my clarinet and pit music, I enter that state and every worry is gone. Of course my mind isn't completely free but perhaps if you do something like this right before you go to sleep, you're still sort of in that blank state and combine that with being tired and it may really help.
If this is really getting to you, there are certainly more techniques you can use in both nighttime and daytime to help control your thoughts. For sleep especially, there's lots of breathing exercises and meditation you can do, again to bring you into a more blanker state so sleep is easier.
You can always PM me if you're interested in some of those meditation like exercises or more ways of controlling your mind, though it will involve lots of effort and fighting on your part.
I say if you even accomplish the first step of accepting your worry is great. Combine that with doing stuff about what you can and having little saviors that free your mind and then just accept you're an adolescent and it is quite understandable to have a lot on your mind. I wouldn't say age even has so much to do with it as does life experiences and personality.
Good luck!
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