Oh gosh I hope your okay! Sometimes I panic for no reason, I used to get severe heart palpatations when I played soccer from anxiety as well. I got an ultrasound and nothing was wrong. I'd say your right in quitting smoking thats bound to improve your gerd and ibs thing as well. Some days also I seem to have a panic attack for an extensive period of time - like a niggling feeling that never quite subsides for a while. Its fairly mild but you are probably just panicking about something to do with your health if you are having ibs and such.
Definately quit smoking though! I smoke when I go out (which is rare at the moment though) and it takes me days to feel normal after just a few.