Advice?

My boyfriend and I have been together for nearly a year. We talk about marriage and babies all the time. He says he wants to start our family within the next 5 years and of course we'd have to be married before then. I am 18 and he is 19 and I know people will probably say that's too young but I don't feel that way at all about it. Anyway he says that he isn't wanting to get married for a couple years and I agree but I really just want to have a long engagement. He knows that but he says he wants to get me a nice ring and doesn't have the money now but I told him I don't want anything expensive I just want to be able to have our love shown on my finger. How do I get him to want to ask me to marry him? Marrying him and having his babies is like all I think about. I have baby fever so bad but I do realize we need to wait for that. But we don't have to wait to get engaged.. What do I do?