False positive?

Has anyone used the First Response pregnancy test and gotten a false positive? Im not even sure if thats what to call it.. AF was no where to be found for 4 days, so i tested. It was a faint line that got lighter after a bit, but still visible, so i left it. Then maybe an hour later i got what i am assuming was af. It was like satan opened the flood gates to hell. So just to ease my mind, i tested the next day and it was positive as well. Im really unsure what to think.. maybe it was a bad batch of tests?