Hi Hoping - I had a similar thing where I was supposed to be 7 weeks and the sac only measured 5.3 weeks. When I went back two weeks later they found an embryo with a good strong heartbeat though they said it only measured 6 weeks. I think some of these early scans are a bit confusing and can be misleading. My doctor said they can be a week out even at this stage. Hope things go smoothly in the next two weeks and you get to see your bub and a good heartbeat.