HCG not get doubled in 2 weeks

Monika
Please help ladies!! I am scared. My HCG level at 4 week 5 days was 8900. Which doctors said its very good and confirmed my pregnancy and then at 6 weeks I went to gyne. The lab result at 6 weeks said HCG only at 15k. I heard it should double every 2-3 days. So I am bit worried. I am in China right now and because of language issues. I talk to my doctor through a translator. It's bit messy. So any suggestion is valuable. My progesterone is 59 at 6 weeks.