I'm not sure if Dr Garret Smith counts as a credible source of information but he says that constipation from taking sequestrants like clay and activated charcoal is due to insufficient bile flow. I think there might be some truth to it, when my liver was very congested I could not tolerate much fiber from beans or oatmeal at all without getting an "intoxication effect". Have you tried the hot water protocol to stimulate bile flow?
During Winter and Fall especially when it's colder, I always drank warm water...lol, even before I knew it was a thing.
Now anything warm (water, food) adds to nausea. I have to drink water at room temp.