I have IBS (Irritable Bowel Syndrome). I think lots of survivors of abuse have it.
My history: I remember having lots of diarrhea even when I was 10. Even as a child, I took Peptol Bismol.
When I was about 40 an excellent specialist recommended that I take large doses of psyllium powder. I found a store manager who ordered this stuff for me in 5 pound bags. It really helped to stabilize my hyper-active large intestine. Even so, I experienced some deterioration of the descending large intestine. http://jamieriderbush.hubpages.com/hub/Best-Ways-to-Improve-Bowel-Regularity-Naturally
The large intestine is not made to come in contact with the powerful digestive juices from the stomach, so if they don't stay in the small intestine long enough to be neutralized, the juices start to digest the inner lining of the large intestine.
I have had good results with keeping a food diary. Write down the foods you eat every day. If you are trying to lose weight, also make note of the amounts you eat. Take note of the foods which cause digestive upset. In my case I have found: peanut butter, pork products, and milk products. Elimination of these has greatly helped the diarrhea problem.
Counseling has helped a lot as my inner tensions get relieved.
I have more recently found that a single dose of Advil PM when I go to bed promotes sleep, promotes relaxation of my digestive system, helps with the food allergies, and helps with the chronic inflammation from the constant intestinal irritation. Advil is ibuprofen and it is a powerful anti-inflammatory drug. You don't need a prescription for this. Make sure that you can handle it before you take this.