I wanted to let you know that you're not alone. Many other people, including my husband and I, have struggled with NFP. We've had times when abstinence lasted a couple months, and even regular cycles have been sometimes difficult, especially for my husband, but sometimes for me as well. I don't think NFP is really what is causing your difficulties.
From experience, let me assure you that using artificial birth control and being able to "have sex whenever you want" does not solve problems like yours and your wife's. Being able to be "spontaneous" isn't a solution to complete lack of desire. My husband and I used the Pill during the early part of our marriage, and we actually had more sexual problems then than with NFP. Couples having difficulties with relations is probably more common than you think. In a study I recently saw, 49% of the women reported sexual problems or having no enjoyment from sex whatsoever; 41% of men had problems. Having both people wanting the same thing at the same time is very difficult. If you use the Pill, your wife basically gets to have Phase III all the time which includes its lack of libido plus other unpleasant side effects (possibly even fatal ones). All other hormonal birth control has basically the same negatives. Barrier methods are a nuisance to use and kill spontaneity, and they're not particularly effective. You might as well cut corners with NFP. Even if you switched to artificial birth control, your wife's problem would probably not go away, and she might even have additional problems caused by the birth control.
I understand the problem your wife is having, at least to some extent, because I have a similar problem. I don't always want to have relations during Phase III. Often I need help getting into that mood, and I ask my husband for help. Sex should never be something you have to "earn" from your spouse. Obviously your wife has deeper problems than a lack of libido. It is possible that she actually has a physical/biological problem and should see a doctor, or she may have mental and emotional reasons for never wanting sex when you want it and can. The body is only a part of the sexual response. The brain is really crucial. Some scientists consider the mental and emotional processes more important than the physical ones in the sexual response. The fact that a woman's body is more prone to sexual feelings during Phase II isn't everything. I noticed that a long time ago and we have learned to deal with it. You and your wife could too if both of you actually wanted to. Her refusal to take temperatures means a lot. It sounds like she too could be resentful about something.
I hope you both can resolve your problems. Remember that even though you have obviously been suffering, you have been doing the right thing, and using birth control will only create new problems not solve the ones you have. If you work together to solve this, you will. I will pray for you both.
