Spotting

I've been on bc pills for about a year now. I always have my "normal" period on the days I should. About 2 1/2 weeks after my period I started getting sick to stomach, cramping, and lower back pain very bad. I started bleeding red blood, then dark brown and have continued to bleed for 6 days. Breasts sore, lower back pain have continued since then. Never has happened before. Anyone have any suggestions about what's going on??!