What? That makes no sense. Further along how? In seriousness? Or is this about sex?
I've never heard of a guy comparing relationships like that. I think it's idiotic--every relationship is different. Apples and oranges. But maybe he's a thinker, this one. I picture the Rodin sculpture guy sitting on a park bench comparing relationship graphs and holding them up to the sun to see how they line up. "Hmm," he says, "this one isn't as far along as these other two. I should call it off." Then he puts his chin back in his hand to think some more.
Whether he really thinks you should be farther along in your relationship or he's just making excuses to break up with you, the end result is the same: it's over. If you feel like you did something wrong, don't. The bottom line is that he just wasn't feeling it. Life goes on. If this is his way of dumping you because you wouldn't put out soon enough for him, good riddance.
Thanks for the question.