If he can do this to you at the time you needed him the most it makes me wonder what else is there?
And if you don't kick him out now, he will turn it on the other woman, he has already tried to blame you and the cancer. What a sick prick.
He will do it again, and if the OW lied that she didn't know about your breast cancer and she did, well, the two of them are probably waiting till it cools down.
He will arrange couple councelling and be super attentive for the next couple of weeks. Then things will have to go back to 'normal' as in back to work and allowing him out on his phone, but checking up on him, checking everything he does being paranoid. He will then blame you for suffocating him and tell you that you need to let it go, it has been a month now and he is sorry but you are making him feel bad and you are ruining the marriage and that it was your fault for having cancer any way. (all bull shit but he will say it along with other crap.) If he does arrange councelling he will either never get round to it as he know some one else will say he is to blame and if he does go he will say the counceller is against him and siding with you and a bad counceller.
He will then go back to the OW or someone else, more likely that skank. Then either the circle will repeat or he will move out with her, spend money like there is no tomorrow, forget about you and the kids, say he wants you to move out and sell and you deserve nothing and it was all your fault, he never really loved you, but he loves her etc etc
Then you will get harrasment from him and alot more stress and have to file for divorce, then he will say he is sorry, he wants you back, the grass wasn't greener, you are the love of his life- whildt telling the skank the sane story too.
He will tell everyone else the marriage was bad before the cancer and paint you out to be thr baddie.
All the while staying with him is teaching the kids it is okay to be in a relationship like that and treat others like that. And them having to deal with the fall out too.
And he wont get an sti test he will either say he did and that he is fine or he just wont, so go to the drs now and get that sorted.
Those things will happen if you try to 'work this out' and then he will make you think you are to blame. You are not. All the while clinging on to a glimmer of hope that isnt there-
Someone posted a mid life crises thread -mid life crisis for dummies?? - sorry mods if i am not allowed to refer to this but I think the OP would find it useful and helpful to read.
Best just to chuck him now, go to divorce laywer and make sure you get at least half. You only have 6months to file under adultery.
You are so Stong you don't need this king sized shit dragging you down.