HCG level question - please help if you can?

I miscarried 5 weeks ago - today is 4 weeks to the day that I had a D & C. 5 days after my surgery my levels were at 1557. 9 days after that they dropped all the way down to 123 (HUGE decline in just over a week). Now, 2 weeks since my levels were 123 I am still getting positives which means my levels are still at lest 25. Does it seem odd that my levels would drop over 1400 points in 9 days and not drop 123 points after 2 full weeks? The reason I ask is b/c I am still getting positives and it seems strange that my levels haven't dropped completely after I had such a rapid drop 4 weeks ago. I thought they declined steadily - not lots and then little bits at a time. Is it possible I am pregnant again and the test is showing a new pregnancy? Please share your experiences with HCG levels and miscarriage?