Hormonal imbalance, stress, certain medications as contraceptives, polycystic ovarian syndrome, eating disorders
, vigorous exercise and thyroid disorders
, could also cause delayed period
. You can do a urine pregnancy test, and if it is negative consult a gynecologist.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor.