This is really good advice.
I did a similar thing to you when my DP of nearly 7 years (5 of them living together) failed to 'pop the question' despite me being clear from the beginning it was something I wanted, and he agreed was probably best if we were going to have children together. I was 27, so a bit younger than you.
I pointed out there was a period the following year which would be a good time to get married and he agreed. But in a similarly nonplussed way to your partner. I brought it up a few days later and he told me I was ridiculous to think that was an agreement to marriage. Plus, he believed he needed to propose. I didn't give a stuff about a ring, but it seemed to mean something to him...
So I waited.
We argued and raged over the suject for months as we had reached an impasse. I came up with a deadline in my head but didn't communicate it to him, that I would leave him by if he didn't propose. I even had friends lined up to help me move out.
He proposed with less than 24 hours left. I agreed, but spent a while decompressing from the whole experience.
We are now planning our 10 year wedding anniversairy and have a child and I am really glad we didn't have to split up as we love each other very much.
But your situation is tough OP. Is he being a bit shit as he just doesn't really 'do' weddings and marriage isn't a deal breaker to him (like was the case with my DH) or does he not really want to get married? It is very hard to tell, and he might not even know himself, which makes this situation very cruel.
However, I would have been entirely reasonable to have left him when I planned, if he hadn't met my needs on commitment, tough as it would have been for a while.