Positive test then Negative test...whats going on?

Ok I took a test this morning as soon as I woke up and it was a very very faint positive then I just took a test again and it was negative. My period isnt due for 5 more days. Does this mean I am not pregnant? Or just very early pregnancy? Or another micarriage? I am confused. *also I asked earlier if it was left over hormones from my miscarriage in early Dec but talked to the dr on call today and they said all hcg lvls were gone at last appt so it def a new pregnancy* I am going to retest in the morning but what do you all think is going on?