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

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???