Is it a yeast infection, BV, or an STD

Patient: I have two sexual partners. After having sex once without a condom with one partner, and once at a later date with a condom with the other partner, I noticed that my vagina began to feel and itchy and slightly burning and a little tender. The problem was not that severe but thinking that I would just nip it in the bud I used a one day home yeast infection treatment. I waited several days before having sexual contact again. It has been about two weeks since I took the home medication. Within those two weeks I had an unusual brown spotting that came and went in one day. This spotting happened twice…on two separate occasions, seemingly only after sexual activity including masturbation. The symptoms, including the spotting, went away. I have had contact again with both partners, both unprotected this time. It would appear that my symptoms have returned. I have been itching, burning, and slightly red. I am on birth control, which is the second pack of a new generic alternative to Mononessa. I took three home pregnancy tests just in case – negative. Today I got what seemed to be my period a day early, which is highly unusual for me since I’ve been on the pill, and the consistency of this period is ever so slightly thicker than usual and the blood is very, very dark brown. Could this be more than just a return yeast infection? Could I have BV or an STD? Other than the itching and spotting I have had no unusual vaginal symptoms, no discharge, no odor, etc.