If you did not have intercourse during that time of your menstrual
cycle (12 to 16 days prior to your 1st day of expected period
, its unlikely that you are pregnant. 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.