I need help bringing up marriage.?

I have been in my relationship for 2 years. We have talked about spending our lives together what are plans are when we retire basically everything except marriage. About a year into our relationship I did briefly bring the subject up just saying I don't want to be one of those couples dating for 10 years then marrying also saying even 5 years is really pushing it. He just said "I won't make you wait that long". I really have a tough time bringing up serious stuff with him. I'm really shy and painfully afraid of rejection and or conflict( I know I need to work on this). It's been 2 years now and finances are not an issue. He is also 38 so I think all his wild oats are officially out. Last night I mustered up the courage to ask "Do you plan on marrying me" He simply said "Yes" then I didn't ask anything else. I really regret not pushing it further as he didn't seem thrown off my question at all. I just froze and didn't know what to say next. Should I bring it up again tonight? I really want to know how much thought he has put into it. I want to know if he has a time line for engagement and marriage yet or if he has just decided he does want to marry me but that's as far as he's gotten. I need some questions I can ask so I don't freeze again.