Strange smell down there...

Hi girls, I recently just had unprotected sex with a guy about 3 days ago, I'm on the jab so I thought I'd be fine. Anyway since then I have had like a really disgusting smell down there... It's not thrush, there's no abnormal discharge it just smells like I haven't washed in about a week! It's so yuck, even when I wash it doesn't mellow the smell... It's so weird maybe it's something to do with his sperm? Right after we had sex I went to the toilet and had a wee, I just dunno what it is or what to do?!