Menorrhagia is the medical term for menstrual periods with abnormally heavy or prolonged bleeding....possible causes are polyps, fibroids,ovarian dysfunction,. Some blood coagulation disorders such as von Willebrand's disease etc,uterine cancer, ovarian cancer and cervical cancer etc...Consult nearest gynecologists for clinical examination and evaluation they will do the needful.

If it's been since three months then evaluation is necessary.....

They could be various causes of heavy bleeding--uterine,ovarian,local cervical causes or hormonal imbalance.You need to consult a gynaecologist for further evaluation.

Menorrhagia can have several causes, ranging from thyroid, ovarian disorders to more serious ones like early cancer. Have yourself evaluated at the earliest