It wasn’t till 1854 that the Catholic Church officially held the view that Mary was sinless. And it wasn’t till 1870 that the Catholic Church adopted the position that the pope is infallible. Fairly modern claim with little historical evidence. Why is it that it wasn’t doctrine in the early church?
The following links should assist you in better understanding the Catholic Church’s teaching on the dogma of the Immaculate Conception. If you have any further questions or concerns that are not answered by these links, please contact Catholic Answers directly.