Ultrasound at 8wks

My baby is measuring 9wks2days with a HR 167. 💓💓💓💓Omg I am so happy.🥰🥰🥰 New due date is 12/15/20.

Last week Tuesday I went to the ER for bleeding they said the baby was measuring 7wk2days with a good heart beat(they didn’t tell me what it was) but I am just wondering how the baby can grow from 7wks to 9wks within a week. My LMP was 3/13/20. I also saw the baby move he’s quiet active!!! I am So happy guys!!!! And does any of know why he grew fast do this happen often?