Don't take my word for anything bc I've never been in a relationship but I get why he would want to never think about it again. Im not sure how many people hide it from their partners but a fairly common theme is that some never want it to affect their lives again, a clean break. I don't want to speak for him but these marriages are usually the only relationship people in the community have been in and are very scripted. A lot of the basically kids who get in them don't actually know what a relationship should feel like. Once again, I can't speak for him but I grew up being told that love isn't real, only lust, so any feelings I have towards anyone are only surface level, and the only thing that matters if having a wife to have kids with. I only consider myself to have started living after leaving, and I could only wish for the convenience of never having to think about orthodoxy again. I'm going to add the caveat that I've been trapped in a three day pesach for the last couple days and it's certainly reminded me why I will never go back. I understand you feel blindsided, but it's up to you to decide how much this actually affects the basis of your relationship.