Nausea during sex? possible indicator of pregnancy?

my fiance and i were "doin the dirty" earlier, and i just got so ridiculously nauseous that i had to make him stop. anybody know what couldve caused that? for the past week or so, ive been having a few signs of early pregnancy, heartburn so bad i feel like im having a heart attack, some occasional nausea (usually in the a.m. but sometimes at night too), and a diversion to most foods. boobs feel HUGE too. any opinions? ive got a doctors appt tomorrow to see whats going on, but tonight just got me thinkin' a little too hard...