Sac, Yolk but no baby?

I went to the ER today due to brown bleeding. My last period was 11/8 so I was estimated to be around 7 1/2 weeks along. I got an ultrasound done and the tech could see the sac and the yolk but no baby. She said I could be very early about 4-5 weeks. My HCG levels are in the 5,000’s. Im just so confused as to how my last period and the ultrasound aren’t lining up. The DR said my levels are normal for a 5 week pregnancy and he had no cause for concern with a miscarriage. He sent me in for retesting in 24-48 hrs. Has anyone experienced the same and went into have a healthy pregnancy or should I be expecting the worst? 😣