Scared

I estimate that I am about 7 weeks pregnant according to my LMP. I have a lot of pregnancy symptoms and constant positive home pregnancy test results. I went to obstetrician yesterday. They saw a sac, but no fetus inside. I was told by one doctor there that it probably is a miscarriage. The other doctor there said to come back in a week for blood tests of hcg levels and for another ultrasound. Maybe it’s miscalculated and it’s earlier than I think. Has anyone else gone through this? I’m very confused and scared.