If sex is only to be used for the purpose of procreation, then is it a sin for infertile couples to have sex when they know about their infertility?
From the Catechism:
1654 Spouses to whom God has not granted children can nevertheless have a conjugal life full of meaning, in both human and Christian terms. Their marriage can radiate a fruitfulness of charity, of hospitality, and of sacrifice.
2374 Couples who discover that they are sterile suffer greatly. What will you give me, asks Abraham of God, for I continue childless?164 And Rachel cries to her husband Jacob, Give me children, or I shall die!165 (1654)
2378 A child is not something owed to one, but is a gift. The supreme gift of marriage is a human person. A child may not be considered a piece of property, an idea to which an alleged right to a child would lead. In this area, only the child possesses genuine rights: the right to be the fruit of the specific act of the conjugal love of his parents, and the right to be respected as a person from the moment of his conception.170
2379 The Gospel shows that physical sterility is not an absolute evil. Spouses who still suffer from infertility after exhausting legitimate medical procedures should unite themselves with the Lords Cross, the source of all spiritual fecundity. They can give expression to their generosity by adopting abandoned children or performing demanding services for others.
Sex was made for procreation yes, but God made it feel good, so we can share with our beloved spouse our whole selves. The bible says, it is better to be married than to burn.
As a still fairly young woman, and past childbearing years, I am looking forward to being with the man that God has planned for me. Looking forward to many times of not just playing Pinnacle.