Someone give me some advice

I was on a birth control pill for a couple days but it was causing me to have chest pains so I stopped taking it. I know sometimes that can mess up your cycle. My cycle has been religious on the 28th of every month and I started cramping and bleeding heavily last night. I put in a tampon thinking it was my period and that starting and stopping a birth control pill screwed up my cycle. Well now today I’m still cramping but the blood is literally black/brown and is a very mucusy (sp?) texture. It doesn’t help that my SO and I had a couple occurrences of unprotected sex within the past month. Does this sound like it’s just because of the pill or should I be concerned? I have a history of ovarian cysts and pelvic inflammatory disease.