I'm with you, Nick5. It's extreme and wrongheaded to say that married people can only have sex when you want a child; and it would be irresponsible to have multiple children that you knew you couldn't support.
But I praise God for making fertility and infertility part of the female design. (I don't think I'm exaggerating in saying that the design of human sexuality is brilliant.) It makes it possible for husbands and wives to choose the fertile or the infertile time, and to achieve or avoid pregnancy: as only you and your wife have the right and the wisdom to decide.
As one doctor I know said, "You know what we call women who practice natural cycle birth control? Mothers." It's so hard to predict and get it right--witness my first child. But how happy am I that we goofed!!!!!!!