First pregnancy, empty sac

Hi all. 38/F, It’s my first pregnancy and actually kind of a miracle. I was diagnosed with unexplained infertility and am doing IVF. I have gone through two egg retrievals this year with some bad results as my egg quality is a bit suffering.

During Christmas (around 12/18/, 12/19)my husband and I did the thang 😂 so anyway, my period was supposed to come around 10 days ago. It’s been late and I started having unusual spotting, it’s very very light, and just kind of like old blood, but again very light, no pad needed. I just came back from my Christmas vacation, and it’s not uncommon for my period to be late after traveling, esp if there’s a time zone change, so for the first couple of days I didn’t think much of my late period. Well anyway, I went on a whim and did a pregnancy test to just check and wouldn’t you know it…dark positive line! I went in for a check up yesterday with my gyno. They saw the sac but no yolk. He told me that it could be too early or that it could be a non-viable pregnancy

My cycles are kind of long, 33-35 days. My last period was 12/5 so I’m supposedly 5 weeks along. Hcg is at 8972, progesterone 72.

What are the chances this is a blighted ovum? And anyway I know the risks…but hoping this is the one….does anyone have any insight?