Experts will tell you that sleeping with someone enough will make you chemically fall in love with them. This is why women are bad when it comes to sleepin around. They can't do it without falling for the person they sleep with. (its scientific) once or twice isn't that big a deal but when its all the time you start feeling things for the other person and you start relying on him to be there to make you feel good.
He doesn't have this issue, men are not like that. As a matter of fact men are not naturally manogomis (spelling?) creatures and thus we are created without having to have attachments. Sorry to say this buy men are naturally dogs. However doesn't mean we can't be trained.
You might what to see what he says when you cut off the gravy train. Stop the sex and just hang with him. Tell him what you want out of this and try it that way. Booty calls never last all that long. Either it will turn into a relationship or it will end. Soon. Best thing you can do at this point to keep this person in your life for a lot longer is to take action in making it last.