Haha! The fact that you find it strange is EXACTLY why you can’t see the difference. Think of it like this: God is present when a new life is created correct? A man provides a sperm, a woman provides an egg, and God provides the soul. Is God slinging those souls around from up in a tower through the closed doors of our houses, into our bedrooms and finally into the child? No! If there is any act where he is present it is during sex! After all, it is during sex that we show ourselves to be created in the likeness of God i.e the Trinity. God so loves the Son that this love in and of itself is a new person, the Holy Spirit. A man loves his wife, and God willingly this love forms a new person! Our marriage beds are altars before the Lord, where we come to show him the ultimate act of Love that we are capable of! When you view sex and marriage through the eyes of God, you can then see where the difference lies between contraception and NFP.