I've got the same thing but for me its mostly unrelated to pregnancy I think... I don't know why but me coughing or hearing other people coughing sets off my gag reflex like nothing else does...
I can handle it when people sneeze, snirch, blow nose, barf, do any of those other things... but if I'm out & about & someone starts hacking up a wet lung, I've gotta get out of earshot or I'll start puking just listening to them.
Now that I'm pregnant its enhanced for sure though lol