Why do I only smell fishy after PAINFUL sex??

Whenever I have regular comfortable sex everything’s good. But sometimes when my boyfriend is rough with me and it hurts I get a little swollen and the next day I start having a bad smell that lasts like a week. You could say it’s fishy. It doesn’t itch it just feels raw and sore. It goes away after about a week and everything’s good again. It’s weird cause it only happens when it’s rough, sometimes when it’s dry it hurts and gets raw too.

He never cums in me either.