Is this friend who is a married man cheating?

I am really good friends with this married man at work. I am divorced. We have grown closer in the last year. Sometimes our conversation gets a little personal. We talk about sex. He never ever mentions his wife. He is really good looking. I am the only woman at this company that he is this close to. We do talk about our children and business. We are both workaholics. I have ask him if ever tells his wife about anything talk about. He says he never talks about work or what happens at work. Is he cheating?