Most Helpful Guy
I think for the most part people can't sympathize for you because you are the bad guy. You cheated, broke his heart, and now, that he is with someone and gave you a glimpse of what you fucked up, you want him back. However even if you did mess up really bad, if you know that you truly still love him, and its not nostalgia or excitement about the proposal story, you definitely should try. keep him close as a friend dont entice him to cheat as you did, instead wait to see how his current relationship goes. Just be there for him , if he still loves you too then they won't work out and you can try again. NEVER break someones heart a second time. The first time is terrible enough. please only try if you are confident about your feelings for him.
Most Helpful Girl
You shouldn't try to win him back. You should move on.