I have been having pain behind my umbilicus for about a year and a half. The pain always appears on the first day of my menstrual cycle and continues for up to a week. Occasionally, the pain will appear at other times of the month as well. It hurts to bend at the waist. I went to a doctor, who couldn t find anything wrong. I also had an upper and lower abdominal ultrasound, which also came up negative for problems. However, the pain is not going away, so I m at a loss as to what to try next.