Brother, I feel your pain.  I've cursed NFP many times for long periods of abstinence and lack of spontaneity. Like you, I believe most men using NFP know the pain and frustration of their wives' lack of desire or even aversion to sex during Phases I and III, and the mutual tension, resentment and even real anger that can result. I've often felt that NFP was the cause of problems in my marriage.

The reason I still practice NFP, and even teach it, is because of two experiences. The first is my experience with contraception. I wasn't raised Catholic, nor was my wife. Neither of us was a virgin when we married. We lived together before we married, and we contracepted that whole time.  NFP was part and parcel of both our conversions – our whole outlook on human life changed, and thus our outlook on sex. Before we married, I swore I'd never have kids. It was only the faith that gave me enough hope in a good God to now have five children. 

The second experience that has kept me going with NFP is the memory of the times when sex was so natural and so right and so pleasurable because we were in phase II and we were open to life.  We were not drugged, snipped, tube-tied, or armored against our fertility. It’s a great, great pleasure. I think those experiences have also made my wife more receptive to making love in Phases I and III.  

But it's because the greatest pleasure is reserved to Phase II that I've been more open to life than I otherwise would be, and more likely to question, along with my wife, whether we have serious reasons to postpone another child. When we've had reasons to postpone, it’s been hard… hair pulling, white knuckle hard. And yet I feel like Peter after Jesus gave the bread of life discourse and asked the disciples if they wanted to leave. Peter replied “Where will we go, Lord? We have come to believe that you have the Words of eternal life.” [Note: I didn't confirm the exact words... feel free to correct].  

For us, going back to contraception would be a kind of apostasy from the faith. It would undo our conversion. And I think it would eventually lead to my moral ruin. Contraception never made me more chaste, more pure, or more faithful of heart. Exactly the opposite. I fear what I would become if I reverted. I know I couldn't fulfill my responsibilities as a husband and a father.  Iwould fear for my soul. 

So…. we continue to use, and to teach, NFP. I don't think anyone is in it for the money, or getting rich as a result of NFP. CCL is nonprofit. Teachers are volunteers. My wife and I see it as an apostolate to ourselves and to a world greatly in need of some sanity with regard to sexuality, as evidenced abortion and by one of the fastest growing billion dollar industries in America:  pornography. It's becoming more mainstream and more perverse all at the same time,  seeking ever younger victims.  

I pray my wife and I will persevere to the end in the purity the Catholic Church teaches and Pope John Paul II so ardently taught. NFP seeks to guard that purity during our fertile years. As a weak man, I am truly working out my salvation with fear and trembling, as St. Paul admonishes. When I read the hard sayings of Jesus about the narrow and hard road to heaven, it often gives me comfort to reflect that those of us using NFP certainly aren't on an easy or widely traveled path. I pray you and your wife will consider seriously whatever advice you receive from CCL.