Hi, Dexilant is a PPI, which is used to treat GERD, Gastritis and ulcers. The common side effect of the medication is diarrhea, nausea and Flatulence. Although the rare side effect of the medication is C diff diarrhea, Osteoporosis and Allergic reactions. The change in stool color has not been listed as one of the side effects, The change in stool color is usually is related to our diet. The pain that you are describing could be due to GERD, Gastritis (inflammation of inner layer of stomach), Gallstone, ulcer or Gastroenteritis (infection of stomach or bowel). To make a diagnosis, more information is needed, like do you still have diarrhea, any blood in diarrhea, is it foul smelling, is it greasy, is the pain worse with food, does the pain go anywhere else? Any fever? Is your skin yellow,too? I suggest that you see your family doctor for an evaluation and possible ultrasound of your abdomen. Feel better soon.