Confused

Hey all 💕 so af isn't due till 14th but as like lost of us got too excited to wait to test especially as have felt so many symptoms anyway I know when your testing before af you are supposed to use fmu but have only just brought test so did it a few mins ago the one window said it was a negative but when I took the test apart(just out of curiosity) there was a second line I was just wondering what this meant if anyone has had the same thing 💕