Anxiety, such a mysterious thing, does crazy things to your body and mind, I know Im going through a rough time right now. My anwser to your question would be from my experience that you have probably been suffering with anxiety for a long long time and then one day it manifests into a full on attack. This is what happend to me 2 years ago. Looking back, befor I was diagnosed by a doctor, I know now this has been going on a long time. I am 28 now and my attacks started happening when I was 19, I didn't know what they were and thought I was dieing. I went to the doc and she told me to drink warm milk befor bed and shrugged off my symptoms. I was in the emergency room all the time and I could tell they thought I was crazy. Infact I just learned today that emergencey room doctors call people like us GOMERs " Get out of my emergencey room" Im sorry Im not much help at all, Im still trying to get it together for myself. I think anxiety is something that happens over time, the stress just builds and builds untill your mind shorts out, it get tierd and freaks out. This is the way I feel about it anyways.

I hope I can help you in future post but right now I feel like the blind leading the blind.
Take care

cassie