How long did it take for your HCG level to drop following a chemical?

I had an early miscarriage (6 weeks) in June and now I just had a chemical pregnancy this month. With the miscarriage my HCG levels fell dramatically within 72 hours after bleeding started. I was told to keep testing until I got a negative result just to be sure everything had come out on its on...which it did. With this chemical pregnancy my tests are still faint but definitely still there. They look exactly the same as they did prior to the start of the bleeding which ended a few days ago. I'm starting to worry that maybe something else is going on. I have appt with doctor next week but maybe I should call and try to get in earlier?

So, basically my question is--for those with previous chemical pregnancies--how long did it take for a test to come back negative following your chemical pregnancy?