What Causes Discomfort In Stomach, Vomiting And Extreme Hunger And Thirst?

For three days I have felt really sick to my stomach and feel like I am going to throw up but I never do. I don't have abnormal stool. It may be my period but I have never had this happen during a period. I am not Hungary at all and have a little fever. I am also thirsty all the time. What do I have?