Hi.there are many reasons which causes delayed period like uterine scarring due to some procedures,uterine abnormality, fibroid in uterus or endometriosis,certain medications, hormonal imbalance like thyroid disorders will effect menstrual cycle or pituitary disorders can also affect menstrual cycle or it might be PCOS. Stopping medications causing delayed periods will itself improve your condition.hyperthyroidism or hypothyroidism treatment will help in bringing back the menstrual cycle to normalcy to some extent.If its a PCOS, you may also experience pimples, weight gain, excessive hair growth on your body,sometimes even depression will be there, based on the history you are mentioning I am suspecting hormonal imbalance, so kindly consult a gynecologist for further management.