Maybe just a what if scenario your subconscious has come up with that doesn't actually mean anything. You are happy with your DH. He has clearly moved on. His news may have sparked some memories in your subconscious that put you in her place. I don't think it necessarily means there is unfinished business. Or maybe it's a warning that you do still have feelings for him or vice versa so you may want to watch yourself around him if you want to keep your marriage. Only you can answer that.