Luna, I’m so sorry you’re going through this.
You are in shock, you are traumatised. Please do not think that your reaction is anything other than absolutely normal. I’m really sorry to say that experts in infidelity give a healing time of two to five years and I absolutely agree with that from my own timeline. You’re just starting.
You dont need to even decide whether you want to stay or go. That can come. Right now you do you. You scream, shout, cry and feel everything. The lens in which you view the world has been shattered and you need to find a new lens, that takes time.
Eat, hydrate, exercise, and allow your husband to pick up the pieces you just can’t manage right now.
As for your husband what he did came from a place of selfishness and entitlement, yes mental health is context but not a reason.
It is entirely possible for a cheat to do the work and become a safe partner. Weirdly your husband has actually shown some courage on telling you, vast majority don’t. I know it hurts though.
Go tell him to do his own bloody work. Tell him to read the books, watch the videos, reach out on the forums, and work out what you need to heal. (He can get some counselling, you will need that too). You can watch and wait, heal and then decide based on his actions. A good starting point for you to figure out if you should even consider giving him a chance is ‘how to help my spouse heal from my affair’ not a long book but will help you understand what he needs to do. Surviving infidelity forum is a great support and has a very good wayward section for cheaters who are trying to do better, they don’t hold back.
But, and this is really key, with time you may find out that this is a deal breaker, and for many it is. But you also may find out that actually your values and priorities mean you’d rather stay and work with a remorseful partner, and that OK too! It doesn’t mean you have no respect, or you’re a walkover, or whatever bs I read on here all the time!
I would just caution anyone choosing to stay to really gain a knowledge of infidelity and what true remorse looks like in reality, as many betrayed rugsweep or blame themselves, try harder in the marriage but this doesn’t work.
But right now you do you! I have been there, I know how much you’re hurting, I know the feeling of looking at someone you thought you knew but clearly didn’t at all. Huge hug.