HCG levels slowing down? Please help! 6 weeks pregnant.

So my first HCG quant was on June 30th at 4pm and came back 2716. I went back July 2nd at 8am (two days later) and my blood work came back at 4495. The nurse seemed thrilled with these numbers and my doubling time came out to be 55 hours which is in the normal range. I just got another test done on July 5th at 11pm (went to the ER, still here actually) and he didn't give me my exact number...just said it came back in the 9900's and said it was "low". I'm 6 weeks today. This would be a doubling time of 76 hours. Should I be worried? I thought HCG levels slowed down after they got so high? I have no bleeding or cramping, but no pregnancy symptoms either (I never had pregnancy symptoms though).