Hello Thanks for writing to us with your health concern. See, unwanted 72 has this particular side effect. It can prepone or postpone your normal period by upto a week, sometimes more. SO the period delay is due to the emergency contraceptive most likely. Just to be sure, the pregnancy test should be repeated 3 weeks after unprotected sex. Meanwhile, other reasons for a missed period are - Stress, anxiety, diet or sleep habits that changed recently, weight gain, hypothyroidism, polycystic ovarian disease etc. However, I would not worry much. Wait it out for a week more, then repeat the pregnancy test. AM sure that the period delay is explained by the intake of unwanted 72. Take care.