Sweetie, I know it feels like NC doesn't work. But honestly, you haven't done any of this long enough to know that. I was in my situation a LONG time before things changed. Look at some of the other vets, they were in it way longer. You clock started in August. And unfortunately, every time we break NC, we set that clock back a bit. That is just a sad fact.
In the meantime, you have done WONDERFUL things. And you are so so strong although I know how much you don't feel like that right now. You want people to know how you feel and strong ISN'T it. But there is a disconnect between what you feel and reality at the moment. Although you are crying a lot, that doesn't signal weakness or that you are going crazy or anything of the sort. It's cleansing and it's needed and it's damn brave of you to get on here and to open up the way you do... they way so many do. It's far easier to do nothing. And sweetie, the last approach you took was doing nothing.
There isn't a single thing you can do to change his mind right now. Nothing. Stop thinking about OW. Stop thinking about him. It won't change. Let that go. He needs time and he needs distance. He will get his perspective when he gets that. And for your own sake, don't judge him too harshly. That's not to say that everyone on this board wouldn't love to take him out and thrash him, but don't. For the sake of your daughters, your baby, and yourself, it doesn't help. It hurts you more.
Keep talking. Just keep spilling it out. Even if it is saying or doing things you necessarily shouldn't. There are a whole bunch of people here who care deeply and will take your hand and walk you through it. Just keep talking.