B/C pills can do that to some women. I had one pill I took for 3 months and was bleeding all 3 months. After taking a different pill i didnt have that problem. You should call the doc and let them know. You may need to switch pills.
It could be your body is just adjusting to the pill, sometimes you bleed a little more then usual until your body gets use to it. But if your really concerned and need more information call your g y n for an appt. and go take a pregnancy test. Goodluck and keep me informed.