Try vitamin c... in Canada and I think UK it's recommended for bv. You can get special slow release vitamin c pessaries for it apparently. Also probiotics consumed regularly may help :)
I use to get it constantly during pregnancy. I no longer do, and so happy. It may seem odd, but I found that I was cleaning myself down there TOO WELL. Idk if you do, not to get so personal but its best not to wash the inner part of your V, only the outside and let water run only on the inside because your body naturally cleanses itself which is why we have discharge. You will throw ur PH balance off by washing away the good bacteria, leaving only bad bacteria to infect you. Also, I stopped wearing thong panties, and only 100% cotton panties. I avoid sodas frequently and include yogurt in my diet. All of these things helped me so much. I hope some of one of these things will help you out in preventing BV. Its such a pain! Take care.