anyone else experience and early scan with empty sac???!!

Hey guys! 
So we went to the doctor three days ago for our early scan since we've had a miscarriage before , we were supposed to be 6 weeks and 2 days but my GESTATIONAL SAC measures exactly where it should be in fact a day ahead at 6 weeks 3 days . However, there was no baby ??! There was a little blip that he thought may be a yolk sac but he did t say much and just told us to come back in two weeks for another ultrasound . I see everyone is posting at 6 weeks that they see their babies and hear heart beats 😩 it's not possible that I'm not as far along as we thought though since he measured the sac and it measures correctly right ? Or is it still possible to not be as far even though the gestational sac measures right on time ?IM FREAKING OUT !! Help!!