Due date revision!??

Kristen • 35 years old mommy to be again! 2nd baby in 2 years. I have a 18 mo daughter and a son who is 14. I just hit the reset button x2!! 😱👑😂💞
At my dr apt I was told my due date was exactly in accordance with my last period. Later that day I had a 4d ultrasound which caught baby stretching out and measured me further along. Then they measured baby's head which put me a week ahead of schedule. Could this be right or do you think it's just a big baby? Daddy is 6'4. Thoughts?