Question?

So we just left the doctor's office and we had to do an ultrasound. I'm 31 weeks and 5 days but the baby's measuring at 35 weeks and is already 5lbs 6ozs. has anyone measured further than they are and had the baby earlier than they should? Of course I know that baby's will come when they want but I'm wondering if he comes in 2 weeks will he be considered 33 weeks and 5 days and possibly go to the NICU or will he be considered 37 weeks?