What Causes Heavy Vaginal Bleeding In Between Menstrual Cycle?

Hi doctor, I m 23 yr old.. I had sex with ma boyfriend in jan march n may evry. Time I took a I-pill hv always had regular period By nw from 3 months I hd irregular heavy bleeding withn ma regular period...n I find dat whenever I walked much...d very next day or hour bleeding started it happened 3 rd tym....plzz...gv me solution....... Is I much serious like....ovary damages...or FSH low..or menopause....