I think it's really sad that the one area where men still seem to be given all the power is over whether or not a couple marry. Considering it's woman who normally take the career and lifestyle cut and the major health risks when a couple have DCs, it's increadibly unfair for a man to deny a woman the security of marriage if she's made it clear she wants it.
However, I was always rather clear with DH, I told him from very early on in our relationship that I wanted DCs by 30 and I wanted to be married to the man I had DCs with before I got pregnant, so that was his timeframe. If he wasn't going to be that man, he should expect me to end the relationship in my late 20s. We got engaged when I wsa 27, married at 28 and had DS when I was 30. (A little behind schedule, but only by a few months...)
The point is, I was brutally honest about what mattered and was prepared to leave him if he wouldn't give me what I wanted.
OP - make it clear you want to get married, tell him you expect to be at least engaged by next Christmas, does he want you to propose to him or will he do it. If he's not happy with that time frame, can he explain why he doesn't want to be married to you.
Make it clear you would be happy without an expensive ring or an expensive wedding day, but aren't happy with being fobbed off forever.
If he really doesn't want to be married, he should be prepared to explain why he doesn't want to be married at all and why he lead you to believe it was a possiblity.