So stressed

I went in for my first Ultrasound on 6/22. Fetus measured at 7weeks 2 days but for some reason the gestational sac was 5weeks 3 days. Has anyone else gone through this? Heart beat was 163 bpm. Could this be an error in the equipment or the ultrasound tech? My anxiety levels are super high right now. Please help and guide me. Doc wants me to go in for another ultrasound in 2 weeks. I cant wait that long. I am losing my patience.