Hydrogen peroxide douches has worked great for me. The Lactobicillis (sp) actually produces hydrogen peroxide naturally in your vagina. That is what keeps the pH at a healthy level and keeps infection away. Sperm actually has a very high pH and if you are prone to infections, it helps.
Research has found that hydrogen peroxide 30 cc intravaginally daily for seven days is very effective and almost certainly better than metronidazole. The same is true of yogurt. Interestingly, Lactobacilli produce hydrogen peroxide.
Vaginal infections are related to excess progestin. Recurrent infections may be prevented by switching to a less progestational product.
So many things or a combination of things can contribute to infections. I personnally hate the antibiotics they give you for BV. It made me worse in the long run. Good luck.