What Causes Fishy Smell In Vagina After Ejaculation?

hi , just want to ask you probably already had this question before. soo after my bf ejaculates inside me i get fishy smell.i was reading about it and it might just got to do something with pH or is it worth getting checked ? is there any creams or soaps to solve this ''issue''. start getting very upset as he makes jokes about it and i think he doesnt realize its only cuz of him i got that smell .