According to my menstrual calendar my periods are a week late as of today. I had an unprotected sex two days back using rhythm method and pull out method. I had all symptoms of having periods but it feels like missed periods. Previously also, I had similarly condition where I was prescribed progesterone to induce periods. It's been almost a year to that, what could be the possible reasons now? I had a stressful month because of hectic work schedule and had a change in my diet too.