Bleeding abnormally with clotting - period?

I've been on the birth control Sprintec since August 2010. Last month I received my period while I had two pills left in my active week. This month I got it a full week early. It was light and bright red, then it would become dark and brown. Now a week after I had stopped bleeding I am bleeding again this time it is a darker red - like burgundy (hard to explain it) I've been getting some large clots with the ping of blood. It basically streams out of me as I use the restroom (also while I am not using the restroom). It's definitely not spotting. The blood flow is too consistent. Normal cramping and lower back pain like I generally have with my periods. Nothing unbearable our out of the normal as far goes pain. Any insight on what may be happening?