Hi, I found your post and it sounds exactly like my situation
I went through Ivf also.
My HCG levels have been excellent so far.
My first scan was at 5.4 wks: sac only
second scan at 6.2 wks: again, nothing but sac, no yolk sac, nothingl
My next scan I will be 7.2 wks. I am hoping and praying that we will see something. THey told me that since it was an ivf, they KNOW for sure of my dates, so things dont look good. But your story has given me hope!!