That's a common concern, that question of whether you're passing MP or just B&P.
First, I'd say go to the FAQ section. Some people swear by the usefulness of B&P and others think it's just fraud. In the final analysis you'll have to follow your own guidance.
Four months seems like a long time to be expelling MP but then, it took a long time to build up all that gunk. I know Bentonite has some "expansion" qualities and can pick up toxins several times its size. Psyllium also has some expansion properties. But. B&P can only expand/extend so far. Have you been taking so much B&P that it could be equivalent to all the MP you've been expelling? How do you feel? Are you feeling better than before the B&P? Have you addressed any health issues?
Finally, my own feeling is that B&P is a "do no harm" kind of combo. As long as you take it an hour before meals so that it does not interfer with the mineral absorptiton of your food, it is not a problem. On the other hand, continuing life with all that MP could be harmful.