Causes may be uterine fibroids,
miscarriage after a
pregnancy, ectopic
pregnancy, fluctuation in hormone levels, genital infections, polyps, IUD (intrauterine device)use, use of anticoagulant drugs and hypothyroidism.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps.