Flagyl is a medication that is quite helpful for many reasons. It kills different types of bacteria in ones body. Don't be afraid, it may very well shohw signs of wonderful helpful relief. If the Doctor did not tell you DO NOT drink any type of alchol while taking this medicaition. Also eating yogurt with active culture, is quite helpful, while flagyl kills all bacteria in the bowel, yogurt replaces the good bacteria, and that is a good thing.
Bless you, I am sure you will be fine, Ii will keep you in my prayers.