Impending Miscarriage Confusion

Amber

Wanting to know if anyone else has gone through this. Got the first scan last week baby’s heartbeat was 111 and measuring right at 6w 3D and looked good. Started spotting and cramping and the spotting has gotten worse. Also on my ultrasound they saw a bleed in my uterus, but weren’t too concerned. Fast forward to yesterday I had more cramping and spotting so we decided to go to the ER. Well they did ultrasound and baby had grown and heart beat was 126 so had gone up and baby is measuring 6w6d which I was 7weeks 1 day yesterday but the tech said that it’s normal for the sizing to be a few days off. Then we got labs back and HCG has dropped even more down to 2,600. It was 3,926 2 and a half weeks ago. They ruled it as Impending Miscarriage and said to follow up with GYN. Has anyone gone through something similar? I don’t understand how baby can grow and heartbeat be good if my levels are dropping .