My OBGYN wants me to back monday for another HCG test I'm down to 20 last time she check. But took a hpt today and it's…

My OBGYN wants me to back monday for another HCG test I'm down to 20 last time she check. But took a hpt today and it's a very faint positive... so I call my OBGYN and she said my hcg level has to be above 25 to show a positive so it might be left over from my miscarriage but she wasn't sure what to say. So is it possible I could be pregnant again???