Please don't do that. Have you consulted with CCLI or another solid NFP teaching establishment about your NFP practice?
After we figured out how my last pregnancy occurred (again - using NFP) we thought it was taken care of.
The truth is...NFP is not 99% effective. They don't really know how long sperm can live - obviously.
I could 4 -5 more babies trying to "figure it out".
NFP is not for everyone and I'm surprised anyone thought it could be the solution for every couple.
It isn't.