PREG. TEST HELP :)

I took 2 tests and both came back negative after I let them sit for about 2 and a half minutes. And then a few hours later I was about to throw them away when I noticed the faint line in the left slot where it's supposed to show if you're pregnant. It only showed up in this one, so is it an evap line from where it's sat for a few hours, or does it mean I'm pregnant? It only showed up on this one.