Hello my friend...irregular periods 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... back pain may be due to pelvic inflammatory disease or urinary tract infection..So I would suggest you to consult nearest gynecologists for detailed clinical examination and evaluation they will do the needful...grey hairs happens when melanocytes stop producing these pigments, due to increasing age,decreased nourishment,protein deficiency etc your hair starts to lose its natural colour which leads to graying of hair....consult nearest dermatologist they will do the needful.