Psyllium will tend to make you seem more constipated at first as it scours the intestines clean and helps mold them back into shape. It's normal to slow down when first starting fiber supplementation, there are many natural aids to this. Please see my "bowel Management notes" for several natural ways to induce BM's and deal with the psyllium slow-down. :)
It cannot ferment or rot, it's just fiber. Paper doesn't rot now does it? :)