Follow up ultrasound

I had my first ultrasound last Monday, I thought I was 6.5 weeks pregnant. Dr saw the gestation sac and yolk sac but could not say with certainty she saw the embryo. Obviously hearing that would make anyone nervous. Did blood work, first numbers were 13,648. 2 days later blood work was 21,472. Went back today and I so happy to report that not only did the dr see the baby but he measured heartbeat at 128!!! He measured baby at 6.5 weeks so I was a week off. He did see another sac that was empty. He couldn’t say for sure it was another embryo that didn’t develop. Anyone have this happen? An empty sac in addition to a healthy one??