HCG decrease 13 weeks ??

Tia

Hi you guys ! Being that I have been high risk I had lots of ER trips and ultrasounds through my first trimester. Yesterday at 13 weeks my HCG was 38, 000 which at 8 weeks I swore it was around that if not higher like the hundred thousands. My ultrasound last night looked great. Strong heartbeat and active baby measuring a bit ahead. My concern is this HCG . I hear it plateaus eventually but is decrease at 13 weeks normal? I am so worried and cant see my doctor til Friday