my vagina smells after my boyfriend cums in me

I've been dating my boyfriend for a year now, and I have a problem with it smelling down there after we've had sex. we've both been tested and have no STDs. the smell can be compared to a mixture of vegetables and a mild fishy smell. I've used lactic acid tablets (canesbalance) where I take a suppository after every 2/3 times we've had sex and then the smell disappears completely, but then it comes back after we've had sex a couple of times. This is starting to get tiring. what should I do?