I have had sex since divorce, but I would never tell my ex about that fact. There are no points to be scored, the game is over.
But, I am admittedly jealous that she is in a new relationship, whereas I am still in the “completely emotionally fucked” phase post-divorce. I feel unable to establish a new relationship.
I do know that you married on the rebound from being widowed after a long, happy marriage, and TBH even though I don’t know either of you IRL, I can’t be the only one who thought it wasn’t going to last.