How to convince my husband that we are ready for kids

We have been together for 6 years, married for 2. We are able to live comfortably on his income alone, but he wants to go back to school before we start a family. He comes from a broken home and I think that has a lot to do with it. He has told me in the past that he is afraid of us not working out once we have kids because that is what happened with his parents. I have been talking about starting a family for years and he knows how important it is to me. We have talked about not trying not to get pregnant but then he changes his mind. How do I make him understand that having a baby will make us stronger, not weaker, as a couple. We have a pretty darn solid relationship now but I feel like I cannot wait forever. Also, for several years now he has told me we would start in a year, then when that year went by he said one more year and now he's saying 2 more years. What do I do!?