Please help!

Is it possible to get a positive on the early detection test but not on a clear blue digital?? I'm so confused here! Had a miscarriage on nov 29 by DNC and think I may be pregnant again! I had what looked like implantion bleeding on Dec 23 and nothing since I took a couple dollar store tests and all came back negative. Today I bought a first response early test and came back with a vvvfl so then went and bought the digital and came back negative. So my question is could I still possibly be pregnant or is it old hcg from my miscarriage even tho the dollar store tests still came out negative. Any help advice anything would help thank you.