It could be that you have to much fluids around the baby because I was measure n a couple weeks ahead then I had a ultrasound and they said I had to much fluids around him then wen I want back to my doctor appointment I was back to my normal size
I'm measuring about 3 weeks about and my midwife said I was fine. I'm 37+4 and I am measuring at 40
Usually your dates are right. Baby can go through growth spurts causing baby to measure ahead! Sounds like your lil man had a growth spurt. And a week isn't a big deal! :)