I need help!

Okay, I need all the info I can get pleaseeeee?!

I had a miscarriage last month on July 6th. My HCG level was stuck on a 9and never raised. I started to bleed from July 6th to July 11. On August 12 I found out I was pregnant again. Yesterday due to a car accident I had to be taken to the ER where they did blood test and told me my HCG level was 620. I don’t know how far along I am. They told me after ultrasound they didn’t see a sac or anything in general. What is happening? Someone pleaseeeee help me understand. I have a follow up appt with my ob on Thursday but I’m panicking. Am I having another miscarriage ? Am I not pregnant at all? Why is my level at 620. I don’t have any bleeding or any pain like I did when I had the miscarriage. In fact I don’t even know how far along I am 😭 is it bad that they don’t see anything in the ultrasound ?? Ugh.