First Ultrasound Visit

So, I took a pregnancy test 2 weeks ago and it was positive!! My las my period was on 10/17/18. I made an appointment for today 12/14/18. When I called they said I would be about 8 weeks today. They did a vaginal ultrasound, but only saw the sack and a tiny yolk sack. The doctor said it looks more like I’m around 5 weeks. She told me sometimes babies stop growing (miscarriage) and it started to worry me. My doctor told me to come back in a week-10 days, but the receptionist scheduled it for 2 weeks out. I cried all the way home, because I’m nuts so worried. Just wondering if this is normal.