Sacroiliitis and fatigue

Last week, I had this back stiffness, inability to move and I was bent when I tried to walk. Called GI and he attributed it to the fatigue caused by Imuran. Two days later, I started having leg and buttock pain. I googled symptoms and it said sacroiliitis. This word rang a bell as a friend's daughter who has UC got sacroiliitis. If this turns out to he true, I will start wondering whether Remicade is still effective. My hidradenitis suppurativa (autoimmmune skin disorder) is flaring up at the moment. Also, my fistula who has been quiet for some time is starting to act up and there is a lot of pus.