This may not be what you are dealing with but I will share a similar issue that developed @ 3 or 4 months after my takedown. I also started really straining to pass stool. In addition to the difficulty and the soreness, it always felt as though I had to go, so many unsuccessful trips to the bathroom. There was blood from the irritation and also some degree of leaking night and day.
Ultimately my problem was determined to be caused by mucosal prolapse. Loose folds of mucosa sort of occlude the opening and is made worse by straining. What did pass was thin strands often with ridges. There is bacterial overgrowth associated with this, so antibiotics help.
This issue can be identified if an endoscopist is looking for it and uses air during the procedure to simulate pressure. Mine was an 80% occlusion. The diagnosis was confirmed with barium defecogram.
I also had a functional issue but did well after an endoscopic procedure where the loose folds were banded. I opted to defer biofeedback.
I'm one year post take-down and recently have noticed some of the same issue again but much milder. I suspect when I am scoped again later this summer or early fall, the doctor will band some more.
Before the banding procedure I also tried psyllium and found it made things worse. But after the banding I returned to with great success.
CT Barrister's question is important. The surgeons don't all seem to manage the pouch issues consistently. There are some gastroenterologists who specialize. Sometimes you have to travel to find one. But it makes all the difference.