Slow rise hcg and baby measuring two weeks behind?

Was in the er for subchronic hemotomia 5 days ago. Baby has a heartbeat! But went back to OB for checkup yesterday and with the bedside ultrasound machine the baby is measuring two weeks behind. Another ultrasound Monday to be sure, but I kept track of my periods on this app. So I felt sure I was 8 weeks yesterday when only measuring at 6 weeks. Got hcg levels back today and they’re rising slow. In a four day spand they didn’t double but they did increase. Went from 33000 to 48000. Giving more blood tomorrow. Anyone have advise or similar experiences?