Burning vagina ??

So I have regular sex with my boyfriend and it's great, no burning no bleeding, I have a regular period but for some reason, every once in a while i will shower and use my normal summer eves feminine wash and it will just burn when I pee, does anybody know why or if a different feminine wash will be better ? Also, for some reason it smells like fish, so anybody know of a GENTLE wash that will clean and make it smell good without burning me😫😫