Baby not growing

My lmp was 1/28.. I'm only 4m pp at the time. I went for an ultrasound and baby measured exactly 6 weeks.. doctor didnt bother looking for a heartbeat because she said it was too early.. I went for a second opinion today and baby measured 5w6d but we had a heart rate of 107.. I should've been 7 weeks since my last us last week. Baby isn't growing and I'm worried.. has anyone been in the same boat.. outcome? I go next week for another us. My first beta was 9800 last week. I'll find out tomorrow what my numbers are now.