When I tappered off pred the most I tappered down was 10mg at a time. I think going down from 60 to 40 might be causing you to flare up again. It took me longer to tapper that I or my GI wanted and I had to at times go back up 5mg for a week or so then tapper back down...it sucks because you want to get off the pred but it is better to slowly tapper than to go into a full flare again and have to go back up to 60mg...I suggest calling your GI and asking if you need to prolong your tapper by going down 5 or 10mg instead of 20mg at a time. I would tell your doctor your symptoms too...
It took about two months for my all my swelling to go down after stopping the pred but it started to improve within about two weeks...