What Causes Fishy Odor From My Vagina After Having Unprotected Sex?

Hi I recently got into a realtionship and am having frequent sex daily, and sometimes multiple times daily. I am on birth control and my boyfriend ejaculates inside of me. I have noticed that when we have frequent daily multiple sex that it makes my vagina itchy and sometimes smell like fish. I am assuming these are both natural reactions to having sex so frequently, and him elaculating inside of me. What are your thoughts? I obviously didn t have these symptoms when I was not having sex so much everyday