hey gary,
listen - my vagina farts a lot during certain sexual positions - all it is, is your positioning, and the build-up of air from the angle your working at. It can be embarrassing - I was initially embarrassed, but my boyfriend and i laughed it up, and by now - so many years later, i'll just go oops! vagi-fart!! and it'll be over and done with. it's natural, its bodily reactions - don't worry about it. your partner doesn't seem to mind, but maybe you should check out with a doctor to be on the safe side.