NFP is no different from any other method of contraception, other than it is difficult and unreliable. You believe, for no good reason, that "artificial contraception" is evil. Of course it isn't.  That error was foisted on us by unmarried men who believed that sex itself is evil, and had to be "justified" by saying that the only proper way it can be used is for procreation. For example, Augustine, in his De Bono Conjugali, said that a married couple who had intercouse without the express intention of procreation was sinning. 

This attitude is completely wrong. It shows that the men who promulgate this error don't have a clue about the place of sex in marriage.