What Causes Rotten Smell Form My Vagina After Having Sex?

I've had past sex buddies for a few years and I've been tested for any infections and I was clear. Untill this recent partner I'm with, we have had sex a few times. And after the first time we done it, I have a weird odour in my vagina and I know I'm not being paranoid because it's defiantly not normal. It smells rotten but I'm not itchy or anything, please help me.