Miscarriage?

Today I went in for my 7 weeks appointment and the doctor found the yolk sac and there was a little flicker that he saw as well but he said it was too early to confirm and that I might not be as far along as they thought. I will go back next week for another - but am concerned it won’t be good news. Should I have seen something even if I was 6 weeks? Thanks for your advise.