If your illness is active, it might be best to stick to really easy low-impact exercises such as yoga. I'm in remission now and am able to push myself hard in the gym, but back when my illness was active and uncontrolled, I pretty much only did yoga. I did it at home (with the Wii Fit) too so that I would be able to run to the bathroom as needed. Exercise is great and you shouldn't stop altogether, but if what you're doing causes worsening symptoms then that's probably a good sign to tone down the activity and intensity levels.