Getting over panic attacks and stress?

I Used to get panic attacks quite regularly a year ago (about) and I missed my period for a long period of time (for the second time) due to stress but it did not happen again until recently. I missed my period for 3 months and I was ecstatic to get it last week but due to horrible news I've had another panic attack. It comes in the form of excessive burping where I feel chocked and like I need to release something and pain in my sternum bone which feels as if I'm being pulled too tightly by my bra or something but it's not the case. I get some dizziness and general death thoughts and it's horrible! I really thought I'd gotten over it and I don't know what to do?I've been stressed because of exams too which have caused problems with my stomach before and after exams to the point of having to Bend during the exam to feel better. I need help I hate the attacks they cause paranoia and pain and i dont what it anymore!