Boric Acid, Birth Control, & Period..

So, I didn’t have my period for multiple months. I got a yeast infection, which multiple attempts of fluconazole didn’t clear. I was prescribed boric acid twice a day for 6 weeks.. After a couple weeks, I started my birth control pill. This same week, all of a sudden I started bleeding, and then it turned into what I’m assuming is my period... is this normal? I’m assuming that maybe my yeast infection was preventing my period from happening, plus also maybe stress, or some other factors.. but, how come I’m having my period even though I’m taking birth control now? I’m so confused.. it normally stops me from bleeding. Is my birth control going to be wrong for me now since it’s not working properly?.. Thanks in advance!!