It is common to have a positive HPT after a miscarriage because your body still has HCG in it. Did your dr follow your hcg level back to zero? If so, there is a possibility you are pregnant. If not, you might continue to test for a while or call your dr to get a blood hcg level. Take care, and I am sorry for your loss.
I agree with Mapes. Did you get your blood rechecked to make sure your levels went to zero. I would def get your blood work done and in a few days get it re-drawn. If your numbers double every 48-72 hrs that is a pg progressing however levels can be low at the start. Did you take a digital test? Just an fyi my previous obgyn told me your cycle starts on the first day your m/c starts. It may be too soon to tell since you haven't missed your period yet. Def give your dr a call. Good luck and best wishes to you. I'm sorry for your loss....
AP