HCG is only really helpful in very early pregnancy. After approx 8-12 weeks or inbetween there they do actually decrease. Some peoples will decrease alot sooner then others also. If you look at the table for expected HCG levels for the gestation by the 2nd and 3rd trimester HCG is lower then the first trimester so at some stage you would expect to see it dropping. I'd say for the gestation you are (I'm assuming between 8-10weeks) that HCG testing doesn't have its place in reasurring a healthy pregnancy or trying to determine a pregnancy that may be lost. I'd say an ultrasound would be a much better way or seeing what is happening.