Go talk to a dr about it bro. Could be many things. Better to be safe.
Stress will make you feel like youre dying. Ive been having some brutal anxiety attacks. They come out of no where. You can be thinking about the nicest things and BOOM.
I know exactly what you mean. For several years I suffered from anxiety attacks that would totally incapacitate me. Just like you said, they would come right out of the blue. Often times I'd end up laying down, thinking that it was the final straw for me. Usually I'd fall into a deep sleep (from exhaustion) after I calmed down a bit.
Finally, my Wife convinced me to see a Doc. He did a few tests and then sat down with me. I told him all about the episodes, and his answer to me was (I watermelon you not) "You're freaking out." He prescribed some anti-depressants that I started to take.
Took those for about two weeks and then said to myself, "Self, if they make a drug to set your mind straight, then you should be able to handle it on your own."
That was about five years ago. Every now and then I still get that anxious tingle trying to crawl up on me, but I've been successful at keeping it at bay by simply telling myself that I'm not dying, I'm only "freaking out" and can handle the situation.
Good luck to all you guys. Stay strong and maintain a high level of confidence in your abilities to handle what life throws at you.
<S> Melvin