Bleeding during ovulation

I don't know whats going on. I started birth control 3 weeks ago on day 1 of my period as my OB/GYN instructed. 4 days ago I started having really strange spotting. Like brown almost black, thick, and tacky. It's gotten heavier each day. Yesterday I had burning vaginal pain to go along with it. Today it looks like there's more blood with it almost like I'm starting my period (which should be in like 17 more days.) What is going on?