it may occur in women who have anemia i.e low haemoglobin levels,diabetes or thyroid problems. It is also common in women with high levels of a protein called prolactin in their blood...it can be the side effects of certain drugs like oral contraceptives,antipsychotics,antiepileptics...it may be due to poly cystic ovarian disease as well... So I would suggest you to consult nearest gynecologists for detailed clinical examination and evaluation they will do the needful

Menstrual cycle is affected by several factors-stress, exercise, thyroid, PCOS, weight gain. Get an ultrasound pelvis, TSH done. Depending on reports, we can decide whether you need treatment