Hello, and I hope I can help you today. Any woman who is having unprotected sex is at risk for pregnancy. However, pregnancy symptoms vary widely between women, and many of the same symptoms people associate with pregnancy like spotting, breast tenderness, bloating, nausea and mood changes can also been used by other hormonal irregularities, such as missed ovulation. In addition, pelvic pain can also have many causes. Therefore, there is no way to know if you are pregnant based on symptoms. The way you can accurately find out if you are pregnant is by purchasing an over-the-counter urine pregnancy test and following the package directions. If you are not pregnant, irregular menstrual cycles can be caused by weight abnormalities (both too little and too much body fat), stress, certain medical issues, travel, and even worrying about pregnancy. So in summary, you cannot tell if you are pregnant based on how you feel physically. Any woman having unprotected sex, even only once, is at risk for pregnancy. I hope I was able to adequately answer your question today and that my advice was helpful. Best wishes, Dr. Brown