I definitely understand why you don’t want to push it, or end up nagging him into anything. But I also think that as 2 cohabitating, otherwise happy adults, you should be able to have a reasonable and productive discussion about your future together.
He might be taking a little longer to get things going simply because this is a new milestone that’s been introduced. You said yourself that marriage was not something either of you was interested in while dating, and that you’d discussed that. Now, you said he’s fine with being married…okay awesome. But being fine with it and actually doing it after 4 years of NOT going towards that is a lot. I think it’s reasonable for you to want an idea of his timeline, but I also think it’s reasonable for him to need a little more time.
I would sit down with him and have an honest discussion and ask some big questions (and be open to answer any questions/concerns HE has too):
-Can you see yourself being married to me?
-When do you feel comfortable getting engaged/married?
-Does my newfound desire to be married feel comfortable to you, or is this something that you’re legitimately having concerns about?
See what he says, and keep in mind that it might not be what you want to hear. If he honestly and caringly tells you that actually, he was more fine with the way things were–not headed towards marriage–and that he doesn’t know if it’s something he wants (or, he wants to marry you but he needs some time), you’re going to have to do some assessment on your end. Are you okay with things as they are now, regardless of marriage or not? Is your committment level the same?
If after an honest conversation you both come to the conclusion that marriage is either happening, but in the not so near future, OR, it’s not really something he wants, then it’s up to you to decide if you’d rather be with this person unmarried, or hope to find someone else that wants marriage and in the timeframe you’d like.
Just to play devil’s advocate…honestly, because marriage was off the table and because that’s the relationship you and he have had for 4 years, he might deep down not want marriage still. That would have nothing to do with you, or his committment to your relationship; it’s just that for all these years he’s been under the impression that no marriage is okay and a shared value, and now it’s not only a change to “yes, let’s get married,” but all the logistics that go along with it.
Give him some time; I’m sure that’s all he needs. I hope you get the outcome (and proposal/marriage) that you want 🙂