Daveg,
Sounds painful. I would definitely start with a colon cleanse routine, especially using an enema. Also be sure to note what kinds of food give you so much problem. If you are having more trouble with fatty foods, then it could be a problem with your liver not generating bile, which is required to digest fats....but first things first.
I would first start with a couple of enemas - I recommend starting with a coffee enema to stimulate the liver, then a cool water enema flush to clean things out. Then see if you are feeling better. If so, then I would start a colon cleansing program with fiber supplements. If you have a lot of pain when you start the fiber supplement, then I would back off on the fiber dosage and go back to the enemas until you can tolerate the fiber.
You can find a lot of information on colon cleansing and enemas in this colon cleansing guide.