Not to minimize your issue, but it could be as simple as raging hormones and the pressures of being a teen. Getting through puberty into adulthood is hard enough, but when you add in the fact that hormones are all out of whack and your body is changing, plus the added social stress, it's not all that uncommon to feel anxious. Eat well, exercise to burn off the excess cortisol and adrenalin that may be in your system, and get plenty of rest and hopefully you'll feel better. Also, know that what seems important to you now is not that big a deal. You'll understand what I'm talking about when you are an adult and looking back at this time in your life.
There is also a teen section on MedHelp where you can get help that you might consider posting in .