Why do I break NC

Yes I am an idiot! Today he text me to see if things were going to work out with the new place I am renting. I respond!!! Then he tells me about an event at his work he is going to tonite with his new gf
I respond I will see you there, I have been invited as well lol.
He freaks doesn't want his mask coming off at a social event. Why do I do this???? I have some text messages he sent me a few weeks ago that we're very inappropriate . What are u wearing, can I watch you with another guy etc. I told him I was going to forward these messages to his new gf and he says that is not fair!! For a minute there I thought I might be hurting him, yeah right.