What Causes Yeast Infection After Intercourse And Menstruation?

I am 43 female and have been in a monogamous marriage with my husband for 25 years. I have a lot of yeast infections and irritation after my period and after sex. My husband nor I have ever had cold sores but he got 2 bumps on his outer lower lip after giving me oral sex. The bumps came up the day after and now I also have vaginal irritation. I recently tried Rephresh gel for vaginal pH but hasn t helped me at all