What Causes Fishy Smell From My Vagina?

Hi, maRecy I answeor health queries right now ? Please type your query here...about two months now I can smell a fishy smell from my vagina, I started using yougurt and it has help a bit but I find after sex I can smell it again very strong. What can I do to get rid of this. I never had it before and it's making me very unhappy