Hello, and I hope I can help you today. Pregnancy symptoms vary widely between women, and the usual sign of pregnancy that is the most common is a missed menstrual period. It certainly would not be unusual to feel sick after smelling secondhand smoke, as many people have an aversion to that odor for healthy and not pregnant. So if you have not missed a menstrual cycle, and are using protection, the likelihood of your feeling nauseous due to pregnancy and the situation are really nonexistent. You can feel nauseous from many other causes including the food you ate, your blood sugar level, as well as infectious causes like a stomach flu. So I suggest that if you missed your menstrual cycle, at at that time you may perform a urine pregnancy test. I hope that I was adequately able to answer your question today, and that this advice was reassuring. Best wishes, Dr. Brown