YHVH and Jesus are one. Jesus is deep pure union with God. Jesus is love. This is why sex is so attractive. It is the fleshly mirror of intimacy and love built into God's name - Yihvah.
Sex is only right in the context of heterosexual marriage.
Because it mirrors God the creator - its purpose is to create life. This also makes sex a very holy thing. To believe in Christ is to be committed to Him in the Spirit of marriage.