So I had an ultrasound June 10th we saw just a yolk sac and it measured 0.66cm and my OB said I measured just before 6 weeks. Today I had a follow up ultrasound and I should have been 7 weeks 6 days based on lmp. So we saw two yolk sacks this time but only one heartbeat and crl was 5 weeks 6 days and heartbeat was 97. They said it was to low and I have another ultrasound next Wednesday. None of this makes since to me how can I measure the same as before but now have a heartbeat and fetal pole? Based on the ultrasound now I was 4 weeks then; is that even possible?How did they not see two yolk sacs before?