I have IBS-D, so my GI specialist told me a couple of weeks ago. I've had constant loose stools for 2 months now without 1 normal BM. I've had a colonoscopy, stool cultures, blood tests, Upper GI series and small bowel series x-rays. He put me on a high fiber diet, including metamucil (I eat the apple wafers that they make, not bad tasting). My specialist said that the high fiber diet may cause some pain at first. Once your body gets used to it, the pain goes away. I have done this and the pain has gotten better since I've been taking it for 3 weeks now. (I also eat Fiber 1 cereal in the morning.) I'd try to keep up the metamucil intake and hope that the pain subsides. It has helped me a little and hopefully it will for you too.
Have you had presistant diarrhea over an extend period of time without 1 normal stool like I have?