I hope this can provide you with some reassurance while you wait. I went in for a scan on 3/6 not knowing how far along I was after finding out I was pregnant at my annual the week before. All the saw was a gestational sac that measured ~6 weeks. I was booked a second ultrasound for viability which I had yesterday (10 days later) and they were able to see the yolk sac, fetal pole and heartbeat measuring at 6 weeks 5 days. Although now they are a little concerned that my FHR was low, I do have a repeat scan in a week- but its amazing how much difference time can make. I know its really easy to read things and think the worse, so try to keep positive thoughts.