I need advice on how to handle a delicate 'relationship' problem?

Is it fair to an ex to tell them you’re in love with them & want to give the relationship another go?..when they are seemingly moving on with their lives. Perhaps they feel the same, but you’d never know unless you throw your cards on the table. Is it worth taking the risk of upsetting them & yourself by putting it out there?
I’d love some advice on this.