Putrid Smell

So I've been sexually active for the past 2 years and have been with six guys and all has been fine, but I've fallen in love with the guy I'm in a relationship with and never want to leave him but our Sex isn't as good as what it used to be because I'm starting to smell really bad down there. I'm not talking about the normal vaginal discharge smell I'm talking very fishy and strong like a can of cat food. I'm so embarrassed when it does smell like this because he loves going down on me but I don't know why it's happening? It's never happened with the guys I've been with in the past, I don't used scented soaps or chemicals down there and and I wash it out with water. I have been tested before I was with him to check for any STIs and he was checked about 2 sexual partners ago. I have no clue what to do, I'm so embarrassed I'd really like some help + I will be going to the doctor soon 😣