It is possible to pass a little but not a full BM with a partial obstruction. Its possible that you may have scar tissue/stricture from all the inflammation in your bowels or the fistula may be starting to perforate your bowels (symptoms for that are severe abdominal pain, chills, fever, nausea and vomiting) which is a serious matter that should be taken care of right away via emergency room visit. Since its the weekend, use the ER at your disposal (if you experience some or all of the symptoms above or if you simply don't feel right cause you know your body best) and call your GI first thing on Monday morning (if you haven't left them a message already this weekend, please do so because someone is listening to messages over the weekend and only emergency cases get call backs usually). You may require further testing done and quite possibly a medication adjustment.