Sorry to hear about your situation.
From a male perspective, take care of yourself and children if any. It doesnt matter if he is cheating or not, it’s taking care of yourself. Start changing passwords and finances secured. Call it mid-life crisis, mental illness, whatever.. sometimes not everything lasts forever.. you dont need someone to feel good about yourself, it comes from you. It’s how you want to define yourself imo. Stay strong and think long term.