I am posting today, because a great source of sadness for me right now, at 50, is that, while a NO Catholic, my husband and I practiced NFP. Before converting to Catholicism, we used other birth control methods.
We have 7 children and I love them all dearly, but I wonder so many times how many are not here because of our practice of NFP.
Once I decided that I wasn't going to do it anymore, my children started coming around 2 years apart. I guess I can reasonably assume that my body worked that way. But we didn't throw NFP away until after our 4th child was born...and she was born primarily because I felt unhappy doing all the checking and charting.
...
Would we have had 9 or 10 children? More?
Please don't be too upset. God uses even our bad and sinful decisions towards His will. Those souls whom He willed to come into existence in your family have. Now that you've repented, you are forgiven and all is as it should be.
Let's take the analogy of murder. I go out and murder someone. Now, it was in fact God's will that the person whom I murdered should have died that day. But that still makes me guilty as if it had not been. Now, once I repent and am forgiven by God, everything becomes as it should be.
Conversely, if I were to have fornicated and conceived a child out of wedlock, it is still God's will that the child came into existence ... despite His not having willed the sin (St. Augustine uses this example). Same is true of the reverse.
So the guilt is distinguishable from the actual outcome. I am held guilty ... until I repent ... AS IF I had prevented souls from coming into being, but everything in the end falls into line with God's will.
PS -- 2 years in between children is VERY common for those who nurse ... as nursing causes the woman's hormones to change so that there are fewer children. We can't be scrupulous and, say, stop nursing, just so we can have MORE children.