Dealing with anxiety?

I'm in school and I'm coming to a really important time in my education and anxiety has begun to take over my life. I've had it in the past, but never this bad before. I often can't sleep on Sunday's because I'm afraid and before an exam, like today, I can't sleep, again, because I have this gnawing in my stomach that I will not only fail, but that I'll be so tired in the morning of I don't sleep and won't have a clue what to do. It even happens when I don't have exams and it's leaving me sleep deprived. Even in situations where it shouldn't appear, it does! I was at a rock concert and we weren't even in the mosh pit and I just felt sick, panicked and like I couldn't breathe. No method anyone's suggested is working. Help??