I'd suggest reading a book called "NOT Just Friends," by Glass. It's the definitive work on emotional affairs.
Your husband MAY be sincere. He may NOT know why he can't just "get back" his feelings for you, and be happy with someone who he thinks is genuinely a wonderful person. If he will agree to it, get him to read the book as well. It will explain how his contact with OW, and his growing feelings for her, is actually blocking him from having loving feelings towards YOU.
