Blighted Ovum

I had an ultrasound today and they are saying I’m measuring at 8w1d. We only had sex twice and during the time I should have ovulated and based off of those dates I would be 5.5 days. Since they are putting me at 8.1 from my lmp, they are saying that this ultrasound looks like blighted ovum to them.... but I’m seeing something there at the bottom and they said they don’t see that as being anything of substantialness because it’s not a true yolk sac or fetal pole. If I really am only 5.5 weeks then could this be the start of a yolk sac? I’m so confused and upset, this is my first pregnancy and I’m just scared if they are right. I go back on April 30th to have a confirmation ultrasound on if this is truly blighted ovum or not. Anyone have any input?