More water. Lots more. With the psyllium and immediately after taking it. Less bentonite.
Psyllium is a natural, slippery bulking agent. But if you take it without a enough water it will plug you up, temporarily.
Bentonite is clay and is naturally constipating.
If you take two tablespoons of psyllium and about 24 oz. water twice daily and do not have a boa-constrictor-sized bowel movement within 36 hours, something is drastically wrong.
I assume you are doing this routine as a "cleanse."
You should know that most of what is taught on the web and in many alternative health books is absolute nonsense. You do not have pounds and pounds of rock-hard fecal matter caked up along your digestive track. And your intestines are not full of an assortment of worms -- as shown on some websites. In fact, some of the worms shown on those sites are only found in exotic animals. They'll never be found in humans.
The bentonite, mixed with the psyllium, will produce a bowel movement that has in it bands of dark clay. That's what you're seeing. Not ages-old fecal matter being swept out of your colon.
I studied in the Robert Gray School (which taught colon cleansing) in the early '80s. And for awhile was a true believer. His herbal regimen and diet really are quite healing. But after speaking with a number of gastroenterologists and observing several colonoscopies (including four of my own over the years), I came to realize that the myth of the claim that we carry around 20 or more pounds of caked up fecal matter that lines the walls of the colon.
You'll never see it if you watch the video screen as the camera is snaked up the length of a person's colon. You'll occasionally see small pockets with putrid matter. But mostly you'll see pink and reddish tissue.
I was challenged on this assertion once by someone in an audience where I was speaking. He said, "Of course you don't see it during a colonoscopy. You take a powerful laxative before a colonoscopy."
And you do. And after taking that laxative, you don't see 20 pounds of fecal matter evacuate your body. But, beyond that, if this caked-up "toxic" material really existed and all it took to clear it out was one treatment with a laxative (most of which traditionally have been natural and/or herbal in origin) then why do the "detox" proponents insist you need a 6-week or 12-week protocol of various cleansers?
End of rant.
Now.... daily use of psyllium (with PLENTY of water) can be quite helpful -- especially if you suffer from constipation -- but it does take some adjusting to get used to it. The cramping that will come with early use will go away after a few days.
Hope that helps.