Bv every four weeks ...

I been with my boyfriend for four months now & ever since I've been with him I've been experiencing bv. No joke I get this every month -.-  I hate it. It's so disgusting. I've treated it with both the Metrogel & Metranozidol 500mg. Every time it goes always I feel a HUGE relief & feel like it won't come back again... But I'm always wrong. My boyfriend & I are trying to get pregnant. We do have sex everyday & he does cum inside me. Could the cum be messing up my floral... What should I do! Thanks guys