Empty sac but Hcg levels are rising??

I went to the doctor yesterday for my first ultrasound. According to my last period, and the app, I'm 8 weeks and 3 days. They did a transvaginal u.s and there was only a sac. They did bloodwork and just called with the results. When they did bloodwork on the 31st of August, my levels were 3,000. My levels now are 69,000. They scheduled me to come back for another ultrasound on Tuesday. I'm so confused and emotional drained from yesterday and not seeing a baby. Has this happened with anyone else, and what was your outcome?