Does Rapid Increase In HCG Levels Indicate Miscarriage?

I am between seven to nine weeks pregnant. my first hcg level was 1602. two days later 3838. 26 days later they are 30000. I have no symptoms really...breast are a little tender but nothing like they were. scared I had a missed miscarriage. by hcg calculator says my levels are doubling every 8.8 days. does that mean I have probably miscarried