HCG levels wrong?

When I went for my initial blood work to confirm my pregnancy, the HCG levels put me at 6-8 weeks, even though I had anticipated I would be around 12 weeks by then based on my symptoms. I had a miscarriage prior to that and hadn't had another period since so we couldn't go by last period date. When I had an ultrasound, it confirmed that I was further along than the hormone levels showed. I've had 2 ultrasounds since, and all are consistent with showing that the HCG levels were not where they should have been. I had my anatomy scan today and she said the baby looks good, but I still can't help but feel worried that something is going to be wrong with the development since the hormone levels weren't high enough in early pregnancy. Has this happened to anyone? What can this mean?

*don't mind that the ultrasound photos are wrinkled. My 2 year old got her hands on them 🤣