Neither did it work for us, not that we were following Catholic teachings - partner lapsed and me Anglican.  It was more because of a desire to use non invasive methods, chemical and physical.
Anyway, what I don't understand is the manipulation of the method - if making love is for the procreation of children - how come it's OK to weasel past that period of time and then have a free for all when there is no supposed chance of conception?

Or is that a totally naive question?