Glad your H can have no-strings-attached sex whenever he wants and then return to his gf who he happens to be cheating on. Sounds like just the kind of guy you should be chasing, one that doesn't know how to stop cheating. This sounds like a competition to see who can screw him into being with them.
I'd like to point out a few critical things: You are believing what he says and you are also doing a fair amount of mindreading. If he wants to have sex with you, he obviously isn't going to point out how things are great with OW. You believe him when he says things aren't working out because you want to. He knows just how to pull your strings. And he definitely is stringing you along. He probably says the same things to her about you. Does she know that you are having sex with him? I'm sure not. He just gives her a convenient little lie so he can run over to see you.
If you don't want anything more than sex, then I guess keep doing what you are doing because you are certainly getting that. If you want to be treated like I'm sure most wives would prefer (except swingers), you might want to reign it in. What you do is certainly up to you. My opinion is biased by the fact that I personally would never accept sharing my wife with some other guy that is also having sex with her. Call me old fashioned that way.
In the end, it's not the years in your life that count. It's the life in your years. Abraham Lincoln
It is hard to fail, but it is worse never to have tried to succeed. Theodore Roosevelt
