What Could Be The Reason For Non Stop Bleeding?

Hi, I had my regular period on «Dec 02 and finished on Dec 05. From Dec 15 I had heavy bleeding. Doctor gave me medicine for hormonal imbalance. Bleeding lessened on Dec 18 but it was still spotting. From Dec 26 I have bleeding not heavy but bleeding is there. Ultra sound report says everything is normal. From Dec 29 Dr. Started birth control pills but bleeding has not stopped yet can u please tell me whats happening