I really think it's possible that he's just "playing" at having an affair because, really, he's afraid that you are going to have an affair. He's afraid of being hurt in that way so he's hurting you in retaliation for a crime you've only committed in his mind. The fact that you have expressed dissatisfaction with him sexually, implies that if he doesn't shape up you will eventually have sex with another man. Don't get me wrong, I think you are right to take this stand because this is honestly how you feel. I feel the same way myself, but in both of our cases this leaves us with the following paradox. If we aren't willing to leave in order to seek sexual satisfaction, we are always on some level subject to our H's whim on the matter. If we are willing to leave, then our H's can tell themselves something along the line of "Why should I want to have sex with her? She is the kind of woman who would leave a man just because she wasn't getting enough sex" and this thought process can justify the sort of behavior your H is exhibiting. IMO, the only way out is through. This weekend I told my H "Yes, I really do love you and, yes, I really will leave you in order to have a decent sex life. Both things are true.". I also said "Please feel free to find a nice woman who does not want to have sex with you if that is what you want.". The only way around the Madonna/Whore Catch 22 is the Madonna/Whore Catch 22. If a guy only wants to have sex with women who don't want to have sex with him then he's pretty much limiting his sex life to fantasy or the hell that the HD men on this BB experience.
"Tell me, what is it you plan to do with your one wild and precious life?" - Mary Oliver