First let me welcome you to WHL. We are sorry that you need us but, since you do, we are glad that you are here.
As I am sure you know, and are concerned about, there are AI diseases that adfect your bowels however but you mentioned that you have Fibro IBS (Irritable Bowel Syndrome) is actually a symptom of Fibro. that goes undiagnosed way too often. If you do a search here for bowels or diahrea you will find thread after thread on this topic.
There are meds that can help you deal with the symptoms. You might want to talk to your doctor about this