Pain and bleeding possibly from birth control

Patient: I recently started on birth control and am on the third week of it. I haven’t experienced any side effects but recently have had abdominal pain and bleeding occur as my third week ends. At first I thought it was discharge of a red brownish color but now going on my 4th day of pain and bleeding it seems more like blood. I am wondering if I had started my period early or perhaps its something else?

Doctor: