Why do we say Mary was "ever virgin"?
Mary is the powerful symbol of the Catholic's complete acceptance of God's grace.
Imagine yourself on Who Wants to Be a Millionaire? For the milliondollar question Regis asks you: "The virginity of Mary refers to: (a) her Immaculate Conception; (b) the birth of Jesus; (c) a Hollywood movie; or (d) an expensive perfume."
Hopefully no one answered (c) or (d). However, even if you went to Catholic school, chances are you might answer (a), and you would lose. The correct answer is: (b) the birth of Jesus.