Slow rising HCG

I just turned 6 weeks. My first prenatal appt was 5 wks +3. HCG was 1100 then two days later 1256. Doctor is concerned about this slow rising. Has anyone had successful health pregnancy with slow rising HCG? Doc put in for referral for sonogram imaging so I have to make an appointment this week. So scared and emotionally a wreck. No bleeding or pain or sign of miscarriage (I’ve had 1 successful pregnancy already). Still super tired and sore boobs like pregnant.

Any hope stories out there ? Thanks for any input