Hello. You should know that menstrual cycle is under hormonal control. The ovary usually releases one egg (ovulation) each month, and about two weeks after, the uterine lining sheds, resulting in menstruation. If the egg is fertilized, it is implanted into the uterus and menstruation does not occur. However, if ovulation does not occur regularly, the body does not send signals to the uterus to regulate menstruation. Stress, jet lag, lack of sleep and too much exercise can disrupt your hormonal balance and cause a change in your usual menstrual cycle.there are many reasons which causes delayed period like uterine scarring due to some procedures,uterine abnormality,fibroid in uterus, certain medications etc. If its pregnany you can get a urine pregnancy test in your home itself. Stopping medications causing delayed periods will itself improve your condition...Hormonal imbalance like thyroid abnormality can cause it or PCOS( polycystic ovarian syndrome)can also be a cause. 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.