HCG Level

Based off LMP I should be 10w5d but at my US two days ago, baby was measuring 6w3d with no HB yet. HCG levels are 44,322 and I have another ultrasound in one week to make sure baby is growing and to check for a HB. Does anyone know much about HCG levels? Originally the nurse wanted me to have bloodwork 2 days apart to make sure my numbers were increasing. After finding out they were pretty high she said they won’t increase much with the next blood test since I’m at 44,333 now. Thoughts?