Help!!

Alright y'all so. I've been seeing this guy for a few months now- and let me just tell you, he is the only partner I've had in the last 4 or so months. However I think I keep getting BV(bacterial vaginosis). I haven't gone in for a gyno checkup because it seems to clear up after a few days each time. Yes, I know that BV isn't sexually transmitted, but I also know that having sex with multiple partners can through off your pH balance down there. So basically my question is: why do I keep getting BV if I'm only sleeping with one person???