6weeks and no yolk sac

Marie
Hi everyone
So I had a dating scan yesterday. I'm measuring at 6 weeks 3 days. I thought I was  closer to 8 weeks based on my last period. 
So basically he saw the gestational sac (I think it's called) but no yolk sac, fetal pole or fetus. I am absolutely heartbroken. This is the first pregnancy for my husband and I. 
I had my HCG levels re done yesterday too and went in to see my doctor today and she said they are really good and quite high. She wants me to go in another 3 days for more bloods and if they are rising, then my second ultrasound in 2 weeks will "definitely show something"; but if they have dropped then it's bad news. 
I don't know what to do. I am so upset. Has anyone else had similar experiences?