Another possibility is diabetes. Recurring yeast infections and UTI's are often a sign of high blood sugar and the body's inability to processes it.

I suffered with constant yeast infections and UTI's for years before someone finally discovered that I had diabetes and my recurrance rate is fairly insignificant now.

Please don't ignore this possibility because the earlier that diabetes is caught the easier and more effectively it can be treated (it too can be exacerbated by stress).