Well, I'm no doctor, and I'm not at your age yet, but I'm wondering if it could be just a factor of you aging? Or perhaps a part of you being off alcohol?

At any rate, the best thing you can do is see a doctor about it.. They can help you a lot more than my semi-educated guesses. Until then, when it happens, try relaxing, not thinking about it, and breathing deeply and slowly. That helped me when it was an issue during puberty.