He doesn’t want to stop and doesn’t see this as a problem. Some women agree with him and don’t care about porn at all. Some men are like you and see it as demeaning and wrong. You need to leave and find a more likeminded partner. OR accept that this is your life. Nagging him is never going to make him change. People don’t change UNLESS THEY want to. He does not. You can not MAKE someone want to. No amount of ultimatums, pleading, threatening, or psychological tricks are going to make this dude give up fapping to randoms. So you need to leave. Or get used to it.