I've been in your shoes and it will get better. Right now you have to influence your emotions through positive actions.
I wouldn't say anything to him about the birthday. He's open and unrepentant about his "relationship" with OW. His actions are telling you that he doesn't want you. So don't chase what you can't catch. Go do something else.
H 34 W 29 BD 3/12/18 Divorce Busted Spring 19
It is not things that bother us, but the stories we tell ourselves about things.
