Measuring early

I had my first appt on 2/2/21 was measuring 7W1D thought I was 8W1D. Today (2/11/21) I went to a free ultrasound clinic and a girl who was in school training did my ultrasound. Today I was measuring 6W3D. I’d that even possible? It has me totally freaked out. I could see the heart beating but wasnt allowed to listen. She also couldn’t get a measurement of the heart beat.

My first ultrasound was vaginal this one was regular could that have something to do with it?