Relationships

Tia
I started talking to one of my ex-coworkers a while back and at first we were just kind of friends but we have begun having sex and now he thinks I'm in love with them. No matter how hard I try to let them know that I do not love him he just really will not understand. How can I make him understand that I do not love him, that I am NOT in love with him, and that I really don't care to be in a relationship with him??? I've never had anyone insist that I'm in love with them, why is this happening???