Unsure of ultrasound

So I was supposed to have my first OB appt Monday when I got there they said they no longer accept my insurance and since my first 2 pregnancies have ended in miscarriages I went to a clinic to get a ultrasound to try to settle my anxiety. I’m supposed to be 8 weeks but they say my sac is only measuring 5 weeks 6 days they were only able to do an abdominal ultrasound not internal has any one measured 2 weeks behind and all was fine? Could it just be the type of ultrasound isn’t showing everything? Idk what to think