my boyfriend took Flagyl for Clostridium difficile (c-diff) for 10 days, and took culterelle and ate yogurt everyday with it and was getting mostly better, his poop was practically normal, and less gas and less times to the bathroom 1-2 times a day instead of 3-4.

now he's been off the medicine for a few days and its slowly going back to how it was before the medicine.
what does this mean?
what should he do?

he had seen a stomach specialist who diagnosed the c-diff and gave him the medicine.
he feels totally fine, just the bad poop is starting again, no stomach pain or anything.