“...Nowhere do I read the mother of God...”
If Jesus was God, and Mary was his mother, then Mary was the mother of God. Quite simple, really, unless one doesn’t believe that Jesus was Divine.
If Jesus has two separate natures, a human nature and a divine nature, it seems logical that Mary is the mother of the human Jesus but not of the eternal God. Can I explain how one person has two natures? No, not anymore than I can explain how one God had three persons! So, I accept it by faith.