Also have your docotor test your stool for Clostridium difficile among the other general stool test. It can and does cause gas, bloating, constipation, runny stool, pain due to weakening of the colon walls and perforation, and in extreme cases can be quite dangerous if not treated. I have it myself now and it took the doctors 9 months do dianose it. I am on vancomycin now, it helps for a few days but then it start to come back. The only other drug that i know of that might help it is flagyl. good luck
Dark Brown Bm,s are normal, it,s the black , tarry stools you must be concerned about..See your Dr, just to be on the safe side.Good luck
.................Dark brownish or anything that resembles dark blood could be that you may be bleeding in the upper part of your intestines i.e processed blood, therefore, it is imperative that you get another doctor to care for you since the one you have doesnt care much. Also the fact that you have trouble with your BMs may be caused by strictures, you need to get some serious exams done.... blood work, upper GI, etc etc.
Take care.