don't fret, mama...ultrasounds are notoriously inaccurate. I DO have big babies but my first was still smaller than the rest at 8 lbs 9 oz, and that was a good 9 days after my due date. My largest so far was 9 lbs 12 oz and it was not the hardest. Trust your body and know that baby is growing the perfect size! Your body will open, bigger than baby!