I'm so sorry you've been going through this for so long! It is so frustrating when you don't have answers, I know from experience. Black stool indicates bleeding, so I'm sure your doctor will consider adding other medications, but unfortunately it may take a bit longer to get your symptoms under control. When I first had black stools, it took a while for Pentasa and prednisone taken together to work. In the meantime try not to do anything strenuous, don't eat anything with a lot of fiber, and try to keep your stools soft so you won't strain. I would give your doctor a call, just so when you go in the GI is already aware of the situation and will have a game plan for you. Take care, and let us know what you find out.