I can understand your anxiety related to delayed menstrual cycle. Pregnancy is the most common cause of absence of menstruation (amenorrhea). It is most likely if intercourse occurs anywhere from 3 days before ovulation (release of egg from the ovary) until 2-3 days after ovulation. 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.
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. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.