Baby measures bigger??

Hi! So I had my last US at 12w4d and my baby measured 11.2cm (just over 4in) and she said that it’s still measuring 12w4d. However, when I first went in for my confirmation appointment at what I thought was going to be 8w, baby measured 6w5d. So I’m just confused on if maybe the baby is big now or if this size is normal? I’ve looked up measurements by week and I’m just so ahead of them all! Has this happened to anyone else?