When you do have pain, is it down lower (of the stomach)? It sounds as if you have a serious case of constipation. When people have constipation, that blockage generally builds up until finally the body must discard it, thereby forcing it out (diarrhea). As silly as it may sound, I think you should drink a lot of water. You need to get plenty of fluids inside you. You should also keep a food journal (what you eat, every day, and when, etc) for at least a week. If all else fails, definitely see a doctor, or if the pain worsens.