I'm freaking out!!

I'm 40w 5ds and went into today for my week appointment and had an ultrasound done just to make sure my fluid levels were ok. While getting the ultrasound they checked to get a guess on my little ones size.. He's measuring over 9 1/2 lbs!! I had an ultrasound done a month ago and he was almost 7, measuring a little on the larger size but nothing crazy. Today he's in the 90th percentile. I know the ultrasound isn't set in stone and he could be smaller or larger but my Dr made it seem like whatever the difference may be it wouldnt be much. Has anyone had this happen with them and their baby have a much different weight than what they originally thought??