Ultrasound said im 2 weeks behind??

Victoria

I had an emergency ultrasound done on march 28 and i measured at 7w 5d

On friday i went for my "first" ultrasound and she measured me at 10 weeks and 3 days

Im reality if i was following my march 28 measurement i should be approx. 12 weeks today

Why did the ultrasound machine measure me 2 weeks behind? Does this mean something bad? Is the baby growing properly??