I wanted to respond to the man who wrote so resentfully of NFP. I am very sorry for his experience, but a couple of things came to mind as I read the letter. First of all, his wife sounds like she is using sex as a tool to control him. St. Paul says our bodies are no longer our own when we marry, but belong to the other. In other words, that marriage should be a self-sacrificing gift of ourselves to our spouse. I haven't always felt like sex when my spouse did, but I am glad that I have always been open to him.
I was always very fertile and found Phase II very difficult. Many times there were tensions, but a normal, loving couple will look forward to Phase III regardless if it's her most natually erotic time or not. We are to control our bodies, not the other way around. Perhaps there is more going on here, and NFP is not the only culprit. (hint: All-the-time-sex does not make for a better sex life. Abstinence can put a fire into sex when it's time.) Your wife never wanting sex speaks of other problems. I also have had trouble with PMS and other physical things, but it has never stopped me from loving my husband and giving myself as a gift to him. Pray for your spouse, and be unselfish toward her. Maybe your example will bring her around. It means alot to me if my husband helps me when I am tired. His kindness opens my heart to him. Every woman wants to be cherished. This man needs to examine his attitude toward his wife, too.
Finally, I wondered how many children this couple has. Small families require more abstinence. The time during pregnancy, and nursing afterwards can be two or three years of "off time". He might also examine how open they are as a couple to more children.
We have been married 28 years and find NFP as one of the greatest gift God has given to us. We were married as teenagers, and believe that NFP helped us to fight selfishness, and become closer as a couple. I would suggest talking to a trusted counselor, and sort through other issues going on in this marriage.