There is a book called "why men marry some women and not others". If you're a reader, pick it up and it'll do you a world of good. It's the result of an 11 yer study. Basically even when starting out so young, within a year and year and half of dating, a man makes up his mind then if he wants to marry you. it's a yes or no answer. He then decides what he is going to do about it. The thing is though, if the answer is yes, he may set out a on a long winded quest to prepare to marry you. Many times guys think they have to have a long list of things to be able to have a wife and potential family. The wrench to all this is that after about 2 years of dating someone, a man gets acclimated to the situation as it looks then. He loses motivation to get married. In most cases, if they get married after that point, the girl has to nag or force him. The suggestion that was made to women looking at the results of many couples is that about a year and half is a good time to broach the subject with him and let him explain very clearly what he's thinking as some of the times they found men would answer "No" to questions like "Are you thinking about us getting married." Many times, he meant "I have tought of it and decided that in 3 years when this is settled, I'll ask you. " You want a ring and a date set no later than 2 years.
Now, let's look at your situation. He has clearly said that he doesn't beleive in marriage. You need to let him know that you want to get married and not someday but tell him when you do. If someone you get him to agree to marriage I wouldn't go for long winded plans, be quick---no more than 8 months.
If he still does not want to talk about it, keep in mind what I said about the book above. I know a lot of people talk negatively about marriage but your chances of having a lasting relationship falls dramatically if you aren't married. I would suggest after giving someone 7 years of your life, you find someone who wants the same things you do and loves you enough to give you things that are important to you. There are plenty of guys out there like that.