Don't give your heart to a brickhead.
Actually, it depends upon the situation. If the guy is only a friend, maybe he wishes to make the relationship more serious. Conversely, if you are arguing when he says this, its probably his way of saying that you nag.
Slap him and walk away! Lol just kidding, but I don't know how to respond to that. I guess it means he doesn't like you or he really likes you. It depends on how he liked his ex girlfriend. Or maybe you just look like her twin. Sorry I can't answer this for you. :)