High HCG

I just got done with my first round of blood work since I found out I'm pregnant! My first HCG test showed my levels at just over 5,000. Two days later they are now over 10,000. I'm about four and a half weeks today, my last period began May 1. I know I can't be further along because I am seeing a specialist who was doing blood pregnancy tests on me since January. Has anyone else had levels this high? Is this indicative of multiples?