Reoccurring BV

I've had my Mirena IUD put in December 2015. I've been having unprotected sex with my boyfriend for the past 3 yrs. Now all of a sudden I get BV (Bacterial Vaginosis) after almost every time we have sex. And he does not cum in me all the time because I've regulated that. (Maybe 3 out of the many)....I was just wondering if it's only me because I am ready to take it out because it's so FRUSTRATING!!! It's just interesting that all of a sudden now I'm having this problem with my boyfriend of 3 yes smh. Help/advice please