When you next see your pdoc, have him check your blood pressure and have a listen to your heart, just to rule out heart related stuff till you get some insurance or assistance.
I agree with the others, I learned that things that were going on with me were called anxiety/panic attacks though I didn't feel anything was happening so bad that such a thing would happened to me. I guess I've ecome a lot less resilent with age.
I hope you'll pinpoint this and get proper DX or someone help you learn how to cope and survive these moments in a less traumatic manner. It can suck and be scarey at the time, as well.

I'm wishing you lots of luck with this, keep us updated.

(((((((( Tgrs )))))))))))))