Imuran takes several months to become fully effective. I doubt seriously he would take you off it before it even has a chance to work. Nor is swelling a common factor . . . the primary thing they watch for with imuran and 6mp is white count suppression in your bloodwork. And if yuo are having less bleeding, that would be a sign of possible therapuetic effectiveness. And yes he might increase your dose. You should probably investigate other causes for your swelling -- where it is?
If you had a norovirus he could not have treated that anyway . . . all you can do is ride it out.