Missed miscarriage

Hello I'm 11 weeks and 4 days today. I have an ultrasound on Friday. They couldn't find my babys heartbeat. I have no bleeding or anything even almost 2 weeks after that appointment. They said she died at 9 weeks. I had an ultrasound at 8 weeks and 6 days in the er. She was perfect and active. The doctor said she looked great. Could there be a mistake or is this just another missed miscarriage? My ultrasound was less then 5 minutes and it was my 1st ultrasound at the office. I just feel like something is off about everything. I was the sickest I was the days before that doctors appointment.