Good or bad progress?

Hi! Need some thoughts from you all! I have two kids (6 and 3 years old) I’m 35 and I just had a miscarriage in September of this year. Got pregnant again quickly and am now 8w3d. LMP was 10/3. I had an ultrasound on 11/20 where heartbeat was 108 and I measured 6w1d even though I should have been 6w6d. I just had my second ultrasound today. I should be 8w3d but measured 7w6d and heartbeat was 166. My doctor said she is cautiously optimistic, although my dates are a few days behind, she said that they grew in the correct interval from my initial scan. So I was 4/5 days behind on the first ultrasound, and am still 4/5 days behind on this ultrasound, but the measurements between the two ultrasounds was appropriate. Does that make sense? Anyone have a similar experience?! Also don’t have many symptoms but didn’t have many with my first two kids either. Tired, backache, sore boobs, but no nausea/vomiting. Thank youuu 🥹🥹