No baby on ultrasound

I had my first dr app today, according to my last period I should be 8 weeks, but when the dr did the ultrasound there was no baby just a sac, she said to come back in two weeks, but I just can’t seem to stop thinking something is wrong.

Has anyone ever had the same thing happen? If so is it normal to not see the baby on the ultrasound?

Thank you everyone so far who has told me their experiences, I will keep y’all updated, I should’ve added that it said I was measuring 7w1d but the dr said she doesn’t want to use that until I come back in two weeks.

Update:

I started bleeding last night and went to the er. They gave me a pain killer and said everything looked fine. Today I am passing little tiny blood clots, kinda looks like tissue. I’m not sure if I should go back to the dr, or just wait and see if it gets worse. Any advice?

Update: tonight it was confirmed I’m having a miscarriage.