He doesn't know what he wants, and is being as honest as he can I guess.
I think he IS half hoping that you will split up with him, to get him out of this awkward/worrying situation?
Of course, he might feel sad if you BREAK UP WITH HIM, before he comes to a conclusion, but he's obviously willing to take that risk?
I know you don't WANT to lose him, but maybe you will anyway?
So why not put him out of his misery & cut the relationship dead ASAP. If you take control, you will limit your period of hurt, maximise your dignity, and he (hopefully) will suddenly find out how he feels? (He can always come crawling back if he DOES have a change of heart?)
A successful marriage is all about long-term effort/compromises, (not just short term infatuation), but, if/when you DO decide to get married, surely you want to be with someone who can't bear to be/live without you?
So take a big risk & dump him? (Be the brave one if he's too scared?)
I know it's a horrible thought, to be alone again after 4 (good) years, but he might respect you more for taking the decision away from him? And you might be heading for a split soon anyhow?
If you don't split up with him, and the lack of commitment remains, you might never have the opportunity to meet someone else who will truly adore you.
Good luck with whatever you decide/whatever happens. I know it will not an easy time.