Hi there - you probably won't get much sympathy on here but I went through the same thing.
I absolutely adored my boyfriend, was desperate to marry him - and he was just very relaxed about the whole thing.
He simply wasn't ready for years and years - we lived together from 1 year into our relationship but he didn't want to go any further.
He never said he was against marriage or that he wouldn't marry me - it just wasn't what he wanted at that point.
I ummed and ahhed about what to do and there was no way I would propose - to be honest it felt a bit strange and I was worried he might say "no"!
I decided that I loved him so much and wanted to be with him so much that I would rather stay and be with him than say "if you don't marry me I'm off".
Guess what - suddenly - after 9 years - he proposed!
We got married 6 months later - once he'd made his mind up there was no need wait any longer apparently - and we have now been very happily married for more than 14 years.
I understand your frustration and how hurtful it can feel when your boyfriend doesn't seem to want to marry - but I suppose it's the same as when a man isn't so keen on children - you have to decide which is more important to you - getting married or being together?