It can be due to your
thyroid issues...you should maintain your thyroid hormones levels within normal limits... Other possible causes are 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 can 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.