Am i positive or not?????

Deja

my period is about 3 days late so last night i took a pregnancy test & it said negative. I re-checked it today & its reading positive. So i took another one today & it still read negative. I checked it about 6 hours later & its reading positive. Its a faint line but you can still see the line. Are the pregnancy test invalid after a certain amount of time? Could i maybe be too early still? Or is my period just off this month??? Im so confused. HELP!!!!!