Measuring 4 weeks ahead?!

Alexis • We weren't expecting to have a third - but ready or not.....!
Tell me this is common... I have two daughters, 1st was 8 lbs 15 days early, 2nd was 9 lbs 3 days early.. Dr told me Friday I'm measuring 4 weeks ahead. I CANNOT have a 10 lb baby lol, I told the dr he can do it if that's how big this boy is gonna be lol. Anyone else measuring early or had in the past??