Ovulating or not?

I had a miscarriage starting Oct 18th. I was only 4 weeks along so experienced no cramping but spotted until yesterday-so about 4 weeks. I got my levels tested Tuesday and HCG was still at 36. Normally this would be my fertile week and since the spotting stopped I decided to  use an OPK for the hell of it expecting a negative but instead got a firm positive. Do you think I'm actually ovulating, or could it be that I still have low levels of HCG in my system?