Hi Thanks for posting on HCM Stool color depends mostly on what you eat and how long food takes to be eliminated from the digestive tract. Black stool(melena) however always reveals an upper digestive bleeding.With a history of chronic diarrhea and symptoms of gastritis, passing out black stool may be possible. The best way to treat your problem will be to treat the underlying cause.Possible causes may include: bacteria, viral, parasitic digestive infections, lactose intolerance... Because it s not clear what causes irritable bowel syndrome, treatment focuses on the relief of symptoms so that you can live as normally as possible.However, proceeding with a stool exam/culture will be very imoprtant. I will suggest you see your Doctor for examination and a stool exam/culture and an abdominal ultrasound.In the meantime, i will advise you try the following: -Continue with imodium -Avoid high-gas foods -Avoid gluten -Avoid ermentable oligo-, di-, and monosaccharides and polyols -Fiber supplements -Anticholinergic and antispasmodic medications like hyoscyamine (Levsin) and dicyclomine (Bentyl) -Your Doctor may also prescribe Antidepressant medications if you pain and depression -Antibiotics if any argument in favour of infection may be prescribed by your Doctor -Alosetron (Lotronex) and Lubiprostone (Amitiza) are currently drugs of choice in IBS Hope all of this information will help Wish you good health