Did you two ever do any counseling? I think you need to. Do you have health insurance? If so, call the number on your card and ask about your options for therapy. Individual therapy for you would be great too.
I think the biggest concern right now is you’ve lost trust in him. And yeah, moving forward without trust doesn’t work. But idk, it sounds like he lied because he wanted to be with you and was trying to protect you from being hurt. And I’m not sure you demanded total honesty.
Look, after the rough time you two had for years, to the point of getting divorced, and now finding out he lied about this whole relationship he had, you need professional guidance to get through this. Things won’t just magically start working smoothly. This is an uphill climb.