Low HCG and falling progesterone levels

I am 8 weeks pregnant as of yesterday (3/30)and things had been going smoothly, or so I thought.  I've had severe nausea and doc put me on Zofran so I can at least eat and drink some again!

On March 2  my HCG was 11.8 and progesterone 20.4
On March 15- HCG 20,000 and progesterone was only 20.9

However, I did a blood panel at a different lab on March 24 and today the nurse called and said my
HCG levels had only gone up to 60,000 (not as high as they would have liked) and my
Progesterone had dropped ti 11.1

They put me on progesterone supp. that I will do twice a day, but I was wondering if anyone else has this type of experience, where the prog. level dropped that much and still went on to have a successful pregnancy.

I am scheduled for an ultrasound Friday morning, but the waiting is AWFUL and I am so scared!
This is our first and very wanted baby....thanks for any input!