Why is my husband doing this to me?

I am divorcing my husband and have left the home and i found out from my son that he is telling everyone i had an affair when i didn't. Anyone who knows me knows i didn't but anyone who knows of me do not know and i hate that he is slandering my reputation all around town. I live in a small town and word gets around and he knows that. I don't worry about it as i know i am innocent but it still is a nasty thing to do. What should i do and why is he doing this...it is so diabolical. It just shows that i am very correct in divorcing him though..huh? no doubts...