High hCG levels, no baby in ultrasound

I am having a freak out!

I had a dating scan a week ago, as I wasn't sure of the date of my last period.

It seemed to go well. We saw a good sized gestational sac and yolk sac, but no baby.

The technician put me at around four, to four and a half weeks. I wasn't worried about not seeing my baby, as I know five weeks is still very early on.

My doctor got me in to do blood tests, to check my hormone levels, and to talk to me about the risks involved with such an early pregnancy.

I just went back to have the second set of bloods, and my doctor informed me that my hCG levels were a lot higher than she was expecting (around 30,000) and that she was worried that this pregnancy was not viable, as my hormone levels are at a place where we should have seen an embryo during the internal scan.

Now I am really worried, and I know I should try to stay positive, but I feel like I might cry.

This is my first pregnancy, and to be honest, I don't fully understand the levels and what they are meant to mean.

What have your experiences been with this sort of thing?