Who tested negative the first time and then positive a few days later???

I'm curious if there are other people who thought they were pregnant, tested negative, and then tested positive a few days later.

I tested last Friday even though I was supposed to get my period last Tuesday.

But I just stopped the pill, so maybe my hormones are all mixed up and it's just taking a while?? I'll take a second test on Monday since it's already been 37 days.