He has to want it. You can ask him, or tell him, you can express how much it hurts you, how much pain it is causing you, but he has to decide for himself. Reminding him will do nothing for a man that is not yet ready. Even if he stops he will still have the PMO mindset and likely be angry at you for making him stop. “I am only stopping because she threatened to leave me.” Some stop initially based on an ultimatum and come around to seeing that it is good for them as well, others don’t. As hard as this is whether he stops or not is beyond your control. You could ask him everyday or remind him, and he could still look at you and lie to your face, that’s what my ex did. Does it lower the chance of them doing it if you keep asking, for some maybe. But we are thinking with rational non addicted minds, addicted minds do not think that way. Many have to “stop” many times before they admit they are ready to full stop. It’s like alcoholism or drug addiction, relapses are the norm. The only thing you can control is when you stay and when you go. You can set boundaries and if he crosses them then you can leave. Believe me this lack of control is maddening, I know I have been there.