Pregnancy Test Help!!

So last night i took a First Response curved pregnancy test and it was definitely a faint positive! This mornin i took two more of the same brand, both even more faintly positive. But then i took a Clearblue Easy digital and it said Not pregnant😢 why was it a darker line last night, and why would the digital say not pregnant, could the First Response tests be false positives?💔💔 PS: Yesterday was 5 days before my missed period, so today is 4 days before my missed period.