This thread is sad to read.
I have been betrayed. I lost years of my life trying to heal the hurt, pain, shock and grief that he caused. Then the post-separation abuse quite literally nearly killed me.
Even if you leave, happiness is difficult to find. When someone you love and trust betrays you, it doesn't just mess up your relationship, it actually affects your whole ability to trust others, full stop.
So even future relationships are difficult, because you then struggle to trust/relax or let anyone in, for fear of being hurt and let-down again.
I stand by my stance, that cheating on someone you claim to love is the cruelest thing you can do to another human.
It might sound dramatic, but his betrayal destroyed me so profoundly that I am literally only still here because of my children.
I didn't stay with him and I still have a long way to go to heal the wound he caused.
My advice would be: go to therapy, individually, for yourself firstly.
It is crucial you have a safe space to work things out.