Thank you guys SOO much! I never heard of something like this so I got nervous. I appreciate all of your responses!
They use your last period to estimate a time that you ovulated and fell pregnant. As every woman has a different cycle using your due date from your period might be wrong anyway. They put me back almost a week.
If you know your last peorid then there's a lot of apps that will give you a date but the baby will come when he or she wants. I'm leaning that
I've had two due dates the entire pregnancy. My doctor goes with my last period which puts me at 39 weeks and 3 days. The ultrasound says 12/1 for a due date. It's only a week apart so I'm not worried.
I went in at what I thought was my 9 weeks (5 weeks after getting a positive) and my baby measured up to 6 weeks! So they moved my due date and now my baby measures back with my original due date -.- but they won't change it back. So maybe the doctor just wants to be sure.