Nausea is the uncomfortable feeling of needing to vomit, and can be caused by a variety of factors. This is because it is a very complex reaction involving nerves and nerve centers in your brain, your stomach, and other parts of your body, any one of which can result in the sensation of nausea. One very important question in your particular age group is whether or not you are pregnant, as that is an obvious cause of morning sickness.
Other questions that are important have to do with changes in your bowel habits, and if there is any family of abdominal or bowel disorders. Finally, do you personally have any other medical conditions? Any of these would offer clues about the potential cause of your nausea. The sensation of being sick to your stomach can come from causes as diverse as your emotional state, the birth control
pill or contraceptive method that you are (possibly) using, the foods that you eat and any digestion difficulties you might have (such as the possibility of lactose intolerance), and a myriad of other factors or causes, some of which could be serious and should be discussed with your doctor
in person. If you have had weight loss
or other symptoms over that same period of time, please discuss these with your doctor as well.