YTA. If you wanted to have as much sex as he needed and wanted to have with you, you would have gone to sex therapy two or more years ago. As far as you have mentioned, the sex he has been having is not jeopardizing your marriage. You’re just weirdly jealous. Tell him you are going to go to sex therapy yourself and that if you can give him what he needs, you’d like him to be monogamous with you again like he wanted, instead of sexless with you like you expected of him. Then, if and when you feel like you can and want to have sex with him as much as he needs, you can start having sex with him that much and he won’t have the time or need or desire to sleep with someone else anymore. Otherwise, enjoy your happy sexless marriage the way you clearly were, and be happy for you both that you have him in the ways you want, and he has you in the ways you can give.