Hello, and I hope I can help you today. If you performed your pregnancy test correctly, then you can be sure you are not pregnant. Over-the-counter pregnancy tests are just as accurate as those performed in the doctor s office. Women can have a missed menstrual cycle for number of reasons. Some of these include stress, changes in diet or schedule, weight changes, and other hormonal factors. In fact, being worried about pregnancy can increase your stress level to the point that it can make you miss your cycle. Furthermore, being sick with another illness can also create stress on your immune system, and therefore affect your menstrual cycle. So for right now, the best thing I can advise you to do was try to relax and wait for your next cycle to come. Your restlessness may be just due to the anxiety of the situation. If you continue to have nausea and begin vomiting, you may want to see a medical doctor for evaluation. If your menstrual cycle does not resume within three months, you also should see a GYN doctor for evaluation for any hormonal abnormalities and treatment to help your period to come back. I hope I was able to adequately answer your question today, and that my advice was reassuring. Best wishes, Dr. Brown