Help please. 6w ultrasound.

Gwen • I`m 29 years old, pregnant with #3 and dealing with adenomyosis and APS
I had my first ultrasound today. I also had another hcg blood draw this morning. Last week my hcg was at 2000, so if the numbers doubled every 48 hrs, they should have been at 16,000 today, but they were only at 10,600. We were able to see the baby, and a heartbeat today :) The tech said we want to see bpm at 100 at least, and she clocked it at 101. She said it looked like it was faster but she couldn't get a good read on it because I couldn't keep my legs from shaking. My doc came in and said everything looks good, but I'm not as relieved as I'd hoped. Have any of you ladies had numbers and heartbeats around those levels and had things continue to go well? I'm 6w today.