I'm sorry that you are in the situation that you are in. It sucks. He has his cake and is eating it too. Why should he change what he is doing when he know that he has you waiting in the wing. I understand. My WAW was doing the same thing to me.
I suggest you seriously consider backing off. Stop the sex. Stop telling him you love him. Tell him that you want to work on your marriage, but will not engage with him if he can not fully engage with you exclusively. Be strong. You will feel better about yourself. You can not convince him to return to you exclusively. He needs to decide that for himself.
I know that this is so much harder to do than to say. But this is what I have been doing for the last month or so and life is so much easier. I feel that W respects me more.
Me-46;W-42 Together 23 yrs Married 16 S11 S8 S6 02/10/03 Her 1st affair 10/01/06 Sep Bomb 01/01/07 Sep Begins 03/09/07 Her 2nd affair