2 positive tests and 1 negative digital

 i had a d&c because I miscarried 7 weeks ago. I went and got cleared 3 weeks ago From my d&c .My doctor told me my blood levels were back to normal. I started bleeding 4 days ago but it was more like spotting. however  I took a pregnancy test today and 3 minutes later I saw a faint line so I waited 2 hours took another one and the same thing. I went and got the digital clear blue ones from Walmart and it came back not pregnant. I’m not certain if I could be pregnant or if my levels are still dropping and the doctor didn’t realize.   need opinions