7 weeks pregnant

I went to the ER today after a random clot came out this morning followed by some spotting. The spotting is brown now and it never was enough to fill a pad or panty liner. When I went to the ER I had my HCG levels taken and they were 50,000. They did an abdominal ultrasound and couldn’t find a heartbeat. Is this normal at 7 weeks or should it have picked up on a tummy ultrasound? I have a transvaginal ultrasound scheduled for Wednesday but I’m so scared I miscarried.