My MIL has always made snide remarks about my wife and I's marriage, things like "you can always get a new husband, but you'll only have one mother". 

Today we were eating dinner with them and she made a comment saying "the hospital always knows who the mother is, the father could be anyone" now, usually I enjoy banter but my wife had been unfaithful the last year, nothing physical to my knowledge, but here we are. (There's practically a 0% chance its not my kid, me and my wife work together.) 

Now, my wife has spoken to her about these comments before, yet she still makes them. Later on I told my wife I was done with her mother, and that I didn't want her in our child's life (just found out she's pregnant 5 days ago). My wife got pissed and I left saying I was done. I'm having a hard time self reflecting on if I'm wrong here. Later, my wife called me out and took her mother's side saying that her mom had said it from a medical perspective, but everyone in that room knows it wasn't in that context. Help.