Hcg levels falling... Am I for sure miscarrying?

Nikki • TTC baby #2 with PCOS
Hello,
    We recently found out we were pregnant and had some light spotting so my doctor had me come in for an ultrasound.  We measured 5 weeks 1 day and saw the gestational sac and yolk sac.  The doctor said it was implanted high in my uterus so that was a good sign.  Shortly after the transvaginal I had some bright red bleeding and cramping for about an hour and then it quit.  My doctor said that could be normal cervix irritation.  My first hcg draw was 3700.  48 hours it had dropped to 2700.  I was told to expect to miscarry.  It's been a week and I'm still getting strong positive tests.  Is this normal?  I have not passed anything or even bled since but I've been assured this is an impending miscarriage.  Has anyone had theirs drop and rise again or does it take a long time?  Thank you!