Welcome to the forum, Trying to heal, I sincerely hope you find it helpful to be here.
Firstly, it might sound harsh, but I want to say that your wife’s infidelity had nothing to do with your illness or you as a person; there are people out there who gave their marriage everything they had, and were still cheated on, or chose to walk away after doing all they could (and many variants on those themes...). I know it hurts to lose someone you love, but you didn’t make her cheat. I know it’s easier said than done, but please don’t blame yourself for her actions.
Also, your children’s perception of you won’t be the same as the one you have of yourself. They won’t likely be thinking of you as someone to merely be endured. I’m sure, if they knew how you felt and understood, they would want to help you.
You sound like a very caring person. I just get an impression from your post that you need to direct a lot more love and care towards yourself! Trust me, you’re not imposing on anyone by posting here asking for help and advice. It’s A-OK to try meeting your own needs!