diarhea every day for the past 4 years

I have had chronic diarhea for the past 4 years, I have had numerous tests done with no diagnosis other than "possibly stress related". I go to the toilet a minimum of 7 times a day, those are the good days. on bad days I have been 18 times in a single day. I no longer notice the cramping, it is all about the rectal pain now. I take a prescription drug called Lomotil, some days it helps slow it down but it never stops it. the one time the doctor gave me a medication that actually stopped the diarhea was wonderful, unfortunately I was one of the few that suffered from one of the side-effects, a cluster migraine, I cannot remember the name of the drug. I can't sleep well, I worry about an "accident", it has been about 3 years since I have slept more than 2 hours at a time. I have to be having a good day to be able to leave the house and I have to be able to get to a bathroom within minutes. a cough or a sneeze are potential disasters. I have had a colonoscopy, nothing there. as far as I know the only stress I have is the diarhea. I have what I call acid days, those are the bad days, they consist of me going to the toilet and producing small puddles of acid, intense pain begins after the 3rd or 4th visit and increases to the point where I am crying and begging for it to stop, I end up in so much pain that I walk bent over because it hurts too much to walk upright, it usually takes about 8-9 hours before the toilet runs ease up enough for me to be able to stand up straight, is there anything to help with the pain/diarhea? I am almost at my wits end, I have tried every over the counter rectal pain relief, they are better than nothing but not even close to actual relief. diets have not worked either, nor have the fiber concoctions the doctors have given me. any help would be greatly appreciated. I am truly desparate.
Thank You.