Hello, and I hope I can help you today. If you have been having unprotected sex you could have conceived. Many women experience symptoms that are commonly associated with pregnancy such as bloating, breast tenderness, mood changes, spotting and nausea when they have irregular menstrual cycles because the hormonal imbalance that caused you to miss your period causes a buildup of hormones in your system similar to pregnancy. Women can have irregular menstrual cycles for a number of reasons, like some medical conditions, weight loss or gain, travel, and stress. The stress of worrying about pregnancy can even affect your cycle. Also the morning after pill typically produces bleeding 3 to 5 days after taking it. So I suggest you perform an over-the-counter pregnancy test if you miss your period. For the future, if you do not want to get pregnant, I suggest you consider going on daily birth control pills, as the morning after pill will only prevent pregnancy from one episode of unprotected sex. I hope I was able to adequately answer your question today and that my advice was helpful. Best wishes, Dr. Brown