Sore breasts and cramping

I am on the birth control pill and have been for 3 months now going onto my fourth packet now. 2 weeks prior to the end of my third packet I started having sore breasts at first and some lower abdominal cramping followed by nausea. I have had that up until now. Me and my boyfriend had unprotected sex about 2 weeks prior to the symptoms and he did ejaculated inside of me twice. After my third pack I got my period 2 days later when it normally does, but it wans''t a normal period, it was just brown discharge that was like a period. I have finished with my "period" today but in the morning I felt like throwing up and I had really bad cramping. Can any give me some advice on what this may be? Any help or advice will be greatly appreciated.