If God has called you to the vocation of marriage, then get married. Pray, ask for guidance and if God shows you that NFP is an option, then take it. Remember, that NFP is not a way of life, but a “planning” option. God is in charge and you will have the child that God has chosen to give you. Think about this. If we were always concerned with “what ifs”, then there would never be a Jewish child born because it could have Tay-Sachs disease (Jesus included), or there would never be an African child born because it could have Sickle Cell Anemia, or there would never be born a child of a woman over 35 because it could have Down’s
Syndrome, or there could never be born a child… on and on the list could grow. Leave it up to God to determine who is born to you and what His plan is for that child. Again, I say, if you know that you are called to the vocation of marriage, then just let God handle the rest.