Depending on your body, PB shakes can be very constipating. In fact when I go on a PB cleanse I do not have any BM so I always resort to daily enemas to have them.
The Master Cleanse system require SWF because the inventor of this cleanse did not like enemas. The idea of this cleanse is to cleanse which requires have several BMs daily. The laxative tea recommended also adds to the elimination.
It seems that you are somewhat blocked and would be very uncomfortable. My suggestion is for you to take several deeps (large) enemas until your large intestines are empty. For details please read my blog titled "My challenge", link below.