Incoming Challenge: Should I stop my Ex-boyfriend's wedding?

My ex-boyfriend just got engaged.

We are not together for 2 years now but I always somehow thought that we would end up with each other. I knew he was in a relationship but I never thought it's that serious.

Now I am really shocked and kind of devastated. Should I come forward with my feelings? Should I try to stop the wedding? Or just let it go? We haven't talked for almost a year now...