Various factors causing it are endometriosis,ectopic pregnancy,hormone imbalance,endometrial hyperplasia,polyps,use of IUD’s and depo shots, sexually transmitted diseases,PCOS and
malignant pathologies of the uterus.
If you have prolonged bleeding
then it is advisable to consult a gynecologist.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided.