WERE JUST NOT ON THE SAME PAGE

My bf is 25, I'm 28. We've been together for a year and a half. although we haven't been together long in the future I would want marriage and kids. He says he's too young and he's not ready and that I have to wait. I have no problem waiting... im just afraid that our wants right now may affect us a few years down the line & I would hate to waste my time because I'm older and would rather have kids before I'm 33 at least. I don't want to wait and still wait and not have everything workout. I talked to him and he says he doesn't know when we are going to take that next step. He even thinks moving in after 1 year of being together is too soon. What should I do?