Kenny, did you try to use a catheter to emty, either with or without injecting water?
I found a post here in the forum with a problem that sounded similar:
Of course your trouble may have a completely different reason, but it shows that such problems can be difficult to identify. Even CT scans may not be able to show the problem in case of twists or a prolapse of the pouch. At least it should clarify how far down there are distended portions of the bowel and if the pouch itself is likely to be blamed.
If you have a prolapse you might be able to push the "valve" open by a catheter and empty that way.
If everything fails, a surgery would help to get things straight and avoid suffering for much longer.
Hope you get better soon.