Possible blighted ovum

Just went for my first ultrasound at what I thought was 7 wks. The us tech saw a sac that measures 6 wks but no baby. My husband and I spoke with the doctor who told us not to worry yet because he sees babies pop up on ultrasounds but this could also be a blighted ovum. I have to go back next Thursday so a f/u. Just so frustrating because I've had ALL the pregnancy symptoms and we had a miscarriage last December. So sad 😔