Exactly. The Bible only mentions Mary being a virgin at the time of Jesus’s conception. That’s it. Period.
And I also know some Catholics who also think that Mary herself was conceived of an immaculate conception, although there is no mention of this anywhere in the Bible that I can find.
That’s a second Marian dogma you have denied/questioned.
“And I also know some Catholics who also think that Mary herself was conceived of an immaculate conception....”
what does ‘conceived of an Immaculate Conception’ mean?
Are you referring to the Catholic belief that Mary did not ever have original sin on her soul when she was conceived in her mother, Anna’s, womb? Immaculate Conception refers to the status of her soul being free from sin - as a special creation of God in preparation of her role as the Mother of our Savior, Jesus Christ.
IC in no way refers to the biological circumstances of Mary’s conception. She had early parents just like you and I. Tradition names them as Joachim and Anna.