One of the things I see with women who have chronic yeast infections is an over growth of yeast or candida in the gastrointestinal tract. We dont know the exact mechanism but anytime there is yeast in the vagina that continues to come back after treatment there is almost always an imbalance in the GI tract as well.
My suggestion to you is to visit a qualified Naturopathic Doctor in your area and look into getting tested and treated. www.naturopathic.org is a good resource for finding a qualified doctor in your area.
Good luck and let us know how things evolve.