I got my BFP immediately following an early miscarriage so my doc ordered an ultrasound for dating. When I went in for it I thought I should be 6w1d and I only measured 5w2d. I was so scared and worried that something was wrong. When I went to see my doc last Monday she said that the ultrasound tech had recommended a repeat us 2-3 weeks later since it had been so early and they couldn't see much (thank you wonderful us tech!). I went back in last Thursday (2 weeks after the initial us) and measured 9w3d which bumps my due date to Feb. 26, 2 days earlier than originally thought. I got to see the heartbeat too. It was so reassuring to know everything is looking good!