I will suggest you try to have more fun with him just by going out to clubs or bars, see that he can have fun with you also you know. He is probbaly just looking for someone to have more things in common. Don't approach him yet, not until you try having fun, then if it continues approach him and tell him that you know what is going on. Maybe you'll want to try a open relationship, i doubt it cuz it sounds like you really like him. Therefore a good solution is letting him know that you can also play that game and post things up for hook up. That will make him realize that he doesn't' want to loose you.