eep, I'd be scared to get vinegar anywhere near my vulva, let alone douche with it (I know, diluted and all, but still)
I think it's hilarious how men can't figure out why the scent changes down there after you start having sex with them.
Sounds like your boyfriend is the one with the problem - but if your worried try drinking pineapple juice for a few days (works for men too). Good luck with your pregnancy.
It could be possible that you are allergic to semen it does happen. You should probably look into this as allergies can increase. Infact i recomend you do, just because it cant be healthy, or even pleasant to have to do that every time after sex. *hugs*