This might be different if you were serial fiance, and kept breaking engagement after engagement and were working through some very serious commitment issues, and then I'd only mention it if he actually purposed, and even then maybe not mention the engagements so much as the issue. You've had a life before him, that's not a crime, nor something he has to know everything about.

You can mention it one day in passing, almost as an anecdote. Don't make a big deal out of it, otherwise he will think it is.

no MM is spot on. you cant tell him. not as a jokey anecdote, not five minutes after he gives you a ring, never tell him you dont need to tell him. its not something you need to hide from him its just that there is no need to tell him. theres a sex and the city episode about it where she feels like an emotional slut because she divulged too much too soon to berger. i had a 30 second engagement too, the engagement lasted less time than it took me to unload the ring once i came to my senses. i dont bring it up because it doesn't need to be, nothing wrong with a little mystery, the past is the past. if it ever came up, my family does like to toss in the odd rib on it on occasion, i refer to that experience as "my quick save in my stupid 20's". not saying you are stupid if that is your age bracket, but it takes the committment phobe stigma right off that experience. you would hope that a man would propose to you based on what decisions you make now, not the ones you made yesterday. dont beat yourself up about it either, i've always said, diamonds shouldn't be present at engagements, they do things to a girl that leaves her without the clarity she needs to make an informed decision lol