What Causes Vaginal Itching And Bleeding Post Intake Of Birth Control Pill?

Hi, I am on the pill, and in the last week, I have had breakthrough bleeding, heavy mucus, and in the last few days it has been insanely itchy and hot. I am sexually active with my boyfriend (only person I have had sex with in a year) we use protection 99% of the time. I do get UTI s frequently but this feels nothing like that. Please let me know what I have if you can help.