My reasons for using NFP were threefold:
- Even if it were not morally wrong, I could not use the Pill or other hormonal birth control treatments, since strokes, breast cancer, and ovarian cancer run in my family. My doctor (not an NFP friendly doctor, just one in the know) told me that the Pill can increase risk of blood clots and strokes, and that ovulating as Nature intended is actually GOOD for the body.

- I didn’t want to rely on something outside myself that is, as we all know, not 100% effective anyway! So many women I know put their faith in a pharmaceutical or an OTC birth control option, and it didn’t work.
I would rather be aware of how my body is working and where it’s at, than be ignorant and rely on a chemical or barrier.
- Moral reasons. If God made me to ovulate and be fertile, than why second guess that? Why take a pill or use a device that takes away the natural rhythym of the body? Oh, that’s right…so we are not “inconvenienced” by a child. Well, if one is not financially, physically, or psychologically ready to be a parent, then one shouldn’t be engaging in conduct that could result in a child. IMO.
Those were my reasons. FWIW, before I was married I had been in a relationship in which I was engaging in premarital sex, using OTC birth control, and I was miserable. There was so much anxiety and worry, and the relationship quickly went south.
I have a friend who is a nurse, and she will only use NFP for her birth control–she has no moral issues, really, with hormonal birth control, but she says health-wise, it’s one of the worst things a woman can do to her body. I have known other women who used the Pill, and then when they were ‘ready’ to have children, had to wait at least a year, or more, for their body to start ovulating again!