Clostridium difficile is a bacteria that is very difficult to eradicate with SCD alone. If you are sure that you are doing SCD correctly and you still have problems, then you should get tested for Clostridium difficile.
You might need S Boulardii in order to solve the problem with Clostridium difficile.
More information about Clostridium difficile:
http://www.breakingtheviciouscycle.info/knowledge_base/kb/clostridium_difficile.htm http://www.breakingtheviciouscycle.info/knowledge_base/kb/clostridium_difficile_testing.htm http://www.emedicine.com/MED/topic3412.htm