Any insight on hcg numbers?

Hey ladies. So I had my first hcg draw after some spotting at 17dpo and it went from 386 to 963 on 19dpo so more than doubled in 48 hours. My next draw was at 23dpo and it only rose to 2754 which is about 63 hour doubling time. The nurse basically said it’s good enough now for an ultrasound but I’m worried it didn’t double. I keep seeing after 1200 it doesn’t always double in 48 hours, more like 72 but didn’t know if this was actually the case or what doctors like to see. I had one instance of spotting last night on the toilet paper so of course I’m worried. It has since stopped but I can’t shake the feeling something is wrong. Any insights or previous experiences with this?