I have been taking my birthcontrol for 4 months now- I am half way done with the fourth pack. I am starting my third week tonight and I got my period?? It is a week early?? It is not a heavy period- just light and dark brown discharge I have had sex but he always pulls out before he comes. And I take my birth control every night at 10:00 sharp.. I just don't get this?? Why is my period still not coming on time. It has been early every month