What a hard time it is when you find out the person you are with isn't acting with the same honestly and regard that you are.
I hope you get to take some time to be kind to yourself, and do some healing. I think one thing that can be difficult is rebuilding the capacity to trust others after someone has taken advantage of that trust. And also, trying not to look back in hindsight with "I should have seen that". Maybe... but you were coming from a place of honesty and respect to your relationship-- and I think with that comes a certain amount of faith that the other person is doing the same. Sometimes they are, and sometimes not, but none of that is a reflection on you.