Hello, and I hope I can help you today. Contrary to popular belief, many women can miss a menstrual cycle once in a while for reasons other than pregnancy. Stress, weight changes, differences in your daily schedule, and even worrying about pregnancy can delay your cycle and sometimes even make you skip your period. What I can say for sure, which I hope you find reassuring, is that there is no way that you could be pregnant from an encounter that happened before you had to normal menstrual cycles. However, if you had have sex since your last period, I would recommend performing a pregnancy test as the most common sign of pregnancy is a missed menstrual cycle. What I suggest you do at this time is, if there is no possibility of pregnancy, just try to wait and see what happens when you re period would be due this month. If you miss another menstrual cycle, it would be prudent to see a doctor for evaluation, as other hormonal problems and medical issues can also be a reason why your menstrual cycle skipped. I hope I was able to adequately answer your question today, and that my advice was reassuring. Best wishes, Dr. Brown