HCG Levels

I found out i was pregnant on 9/20/22, first U/S was on 10/3/22. Here i am super excited since TOS would be our first after trying for two years. Our tech does the ultrasound but then walks out saying that she will bring the doctor in. Doctor says that based on my LMP i should be spend 8 weeks but baby is measuring at 6 weeks 6 days and no heart beat detected. I explained to her that I have a very irregular period so I’m never clear on when i ovulate. Doctor said it could be early gestation. She orders lab to check for rising/lowering HCG levels to hopefully rule out a miscarry. My first lab on 10/3/22 came back to 12,656. Second on 10/5/22 was 18,493 and the third one was on 10/7/22 was 28,304. I also have another U/S schedule for 10/12/22. Is this a good rise, should I still worry?