I really think the key is to bare your souls to each other and share your innermost feelings. To do that you both need to hold nothing back, and you both need to learn to listen to the other. The intimacy that grows out of that will fill the void you are feeling now. Intimacy doesn't necessarily equal a laundry list of sex acts, instead it is an intimate knowledge of your partner's feelings, desires etc. Getting to that point is likely the hardest thing you'll ever do, and it may hurt along the way, but I can tell you from first hand experience that it makes all the difference in the world. It would be worth going to a marriage encounter weekend to help you get started.
What is W's feelings? It sounds like maybe she is extending an olive branch with her willingness to do something (ML) because it pleases you. Your actions are saying that isn't good enough, I want the whole thing. It is like breaking the branch into a million pieces and throwing it back at her. Talk to her, understand HER feelings and where she is coming from. You both need to step out of your comfort zones and meet in the middle. From your posts, it sounds like she's stepped in that direction but you steadfastly refuse to take a step toward her. SOrry if this sound harsh, but I think it is the way it is, and it would probably be pretty much the same if you got a D and found OW.
