Thanks for the advice. Like a lot of the men on here, I often feel taken advantage of, and that my wife has no respect for me, at least no respect for my needs.
I think I will order the NMMNG book. As you can see in my reply above to MJontheMend, I am a very nice guy, and it's getting me nowhere. Somewhere along the line, I think she stopped seeing me as a lover and more of a friend.
I'm so tired of getting my wife to change her ways, I've given up on us. I'm fed up. I don't care anymore. Whatever. I'm done. Even as little as a year ago, I may have given threatening a D a chance, but now, to hell with it. And even if I did, I know how it would go: have sex once or twice to shut me up, and then back to square one. But I would feel even worse than ever.
Anyway, I'm in a really foul mood tonight, and I'm angry that my wife has all this power over me, and I just wish I could walk away.