No fetal pole however there's a yolk sac.

I went to a women's health center and I got an ultra sound at 6 weeks and 1 day. At that time they found a fetal pole and yolk sac and everything looked good. They measured the baby at 5 weeks and 5 days with a heart beat of 122. Two weeks later (Monday) I had an ultra sound at the hospital and it had an yolk sac that measured at 7 weeks and 3 days ( the same as the previous ultra sound just a week or so later)  they also said everything else looked good and healthy however they told me that I missed carried. The doctor told me that he wanted to make sure so he checked my HCG and we found out it was 77,000 he was thinking that it would be under 1,000. So he thought that this was a good sign so I came in today to see if it doubled or went down. The results came back and it only went up 4,000 so I'm at 81,000. They want to do another ultra sound but my doctor told me that since it didn't double in his experience it won't be a healthy pregnancy and believes that I have a blighted ovum. However I don't see how that is possible when there was a baby 2 weeks ago.. Has anyone gone thru this and they had a healthy pregnancy? Please give me some advise I hate this waiting game.