Postpartum pregnancy???

So here I am almost 8 weeks postpartum and NO PERIOD. Well I took a clear blue it was negative but when I got up this morning and it was positive! I know you only read them after a certain time but I was curious (making sure it was still negative). So I got another test the dollar store brand and it was negative. I know I know we was supposed to wait yada yada yada. When does your period come back after you have a baby? What are my chances you think of being pregnant? Has anyone ever had a negative change to positive and still be pregnant? Also I had to reschedule my 6week postpartum check up to this coming Friday so I should know for sure but just wanted to see what y’all experiences was?!