I want to start but.....

I have the stuff to start and Thursday was going to be my first day, but after reading a few other forums, I am now not sure if the Master-Cleanse is the right one to start with. First, there is the P&B (which I am not sure what it does), then there is the liver flush, and to make matters worse, I have a had a week of painful runny stool and now a day with no bowel movement at all. My aim is to clean my colon and bowels as well as get rid of any parasites that may be lurking. Could I do the Master-Cleanse first then at some other later date do a different kind of cleanse???? HELP please.
Vanessa