Has this happened to anyone?

Renea
I went into the doctors today thinking I was 10wks and 2 days but upon getting a ultrasound she saw the baby was only mesursing 9wks and like a day. I didn't get to hear the heart beat but I saw it flickering on the ultrasound. Heart rate was 176. She pushed the due date back. The baby looks big in my opinion for being 9wk 
Just wondering has anyone else experienced something similar?