I think your instincts to do the P&B shakes is right on. Do them as much as you possibly can, and ONLY take herbs to increase peristaltic action (laxatives) when you need to.
Psyllium seed is water-soluble so you usually do not need laxatives when taking it, you just need to drink enough water throughout the day - most people's mistake and cause for constipation. The shake, when done properly, is really all you need to cleanse and strengthen the colon. It, in effect, "scours" the walls of the colon, removing debris. It does not make you dependent on it.
Take as much as you can for about 3-4 weeks and then do the parasite cleanse recommended here, or choose something specific to pinworms. Until then, eat very very simple foods, cooked not raw, mostly hot cereals, soups and fresh-squeezed veggie juices, so that you feed YOU and not the pinworms.