Measuring just under 6 weeks - only gestational sac

Amber

First day of last period: April 8, 2021

Positive OPK: April 24, 2021

Likely Ovulated: April 25, 2021

Last day I had sex was April 25, 2021

Faint Positive pregnancy test: May 6, 2021 (11 dpo) was negative the day prior.

Based on the above dates I should be just over 7 weeks pregnant. I had an abdominal and Transvaginal ultrasound yesterday and my OB called and said they only saw a gestational sac measuring just under 6 weeks. He said it could be a blighted ovum or it could be viable they don’t know. Their going to do another ultrasound and blood work in 2 weeks.

Did anyone else have this? I dont have many pregnancy symptoms at all and I feel like this is going to get my hopes up for another 2 weeks only to be told it’s not viable. Would you not see more than a gestational sac at just under 6 weeks pregnant? I would think you would see a yok sac and if not it’s 100% a blighted ovum??