text: First off, I read that the question was about an upset stomach, not about cramps.  Cramps is a completely different thing.\n\nMenstrual cramps are pain or discomfort in the lower abdomen just before or during a menstrual period. Dysmenorrhea is the medical term for menstrual cramps. \n\nAn upset stomach is just that.  The symptoms of an upset stomach include occasional heartburn, indigestion, a taste of bile in the mouth, pains in the stomach, nausea and then there is Gastritis - meaning inflammation of the stomach.\n \nWhen you menstruate your hormones can over-stimulate the emesis centers of the brainstem resulting in frequent upset stomach. In pregnancy this is known as "morning sickness", this uncomfortable problem tends to be worse when you first wake up, but can happen any time of the day.  Try eating crackers or smaller, more frequent meals.  Try to keep track of what you eat and see if a particular food might be causing it.  Some of the "troublesome foods are coffee, citrus fruits, fatty foods, spicy foods, onions, alcohol and chocolate.