Confusing Results

I took a pregnancy test two days ago which came back negative, and saved the test...looked at it again this morning and now there's a very very faint pink line (thats barely noticeable, and I had to hold it up in a light a certain way to notice it) and one strong pink line...I know the test says to discard after 10 mins...is it possible that the test is really positive even if the test is 2 days old??