Miscarriage?

Adria
So I went the doctor on Tuesday for blood work and my HCG was only 72 (she said with being bout 5 weeks now her expectation would have been in the thousands). I'll go in tomorrow for repeat blood work to see if it's gone up or down.  Did anyone have an experience like this and how did it ten out. If I did miscarry early how long would it take for the hormone to leave my system?