Btw, the Catholic Church is not against birth control because it wants to fill up the planet with people.

The Church is obliged to teach that sex is supposed to be about a man and a woman taking part in God's ecstatic act of creation, a selfless act of love. Sex without being open to life is porn: without the act of self giving and preparedness to receive children, you are left with a corrupted, self-directed form of pleasure.

This is why the Church is not against quite effective natural methods like NFP, because in this method it's the people who change their own behaviour, based on a natural cycle. It's quite effective but does not close fertility in a mechanical way.

Second, if people were really listening to Jesus Christ and the Church, much more people would hear a calling to lead a consecrated life, as a priest or a monk or a nun.