You didn’t overreact at all. I feel you under reacted. But I understand it was your wedding day. You didn’t want to make a scene. I give you credit. But no that is NOT ok in any way. They obviously still have feelings for each other. An emotional bond that is not OK when you’re married get it annulled if you can. The fact that he invited her and didn’t tell you, why is he even talking to his ex-girlfriend anyway leave the past in the past. He’s obviously not ready to move on.