I went for a scan at 5 weeks pregnant and saw only a gestational sac and was told it could be a blighted ovum. I did read up and see that only in 50% of cases is the yolk sac even seen at 5 weeks let alone a foetus, but just the mention that something could be wrong had me stressed for the two weeks I had to wait.
Today I went for another scan - with the doctor still mentioning that she wanted to see if there was even a baby. Sure enough my baby was there (only 8.8mm big) with his/her heart beating well. I was so happy. They said I am 6 weeks 6 days today.
Don't let doctors stress you out too early. They say its their job to give the options, but I don't think they realise the kind of worry we go through. Hang in there.