Ultrasound Wednesday - HCG not doubling

I'm really anxious for my ultrasound on Wednesday, I'll be 7w3d with my 8th pregnancy. I have one living child and the rest of my pregnancies ended around 5-6 weeks (one a missed miscarriage at 9 weeks but baby passed at 6.5 weeks). I got bloodwork with 3 HCG levels last week and my numbers aren't even close to doubling, so we had to schedule an earlier ultrasound to check viability. Previously we were going in March 4th. HCG Monday Wednesday Friday was 30k, 34k, then 47k. I'm honestly not sure what to think based on Fridays number, but anxiously awaiting our ultrasound for answers.