Help!!

Thursday morning I had 2 positive tests one was a line test the other a digital. Last night I got home and I had brown discharge the brown then turned to light pink to red today along with cramping. When I saw the brown discharge I got scared so I took another digital. It said pregnant. A few hours ago when I had heavier bleeding and cramping I took another and it said not pregnant. But I took all 3 of the digital tests apart the top is Thursday the middle is last night and bottom was earlier why is the negative one the one with a darker line but the one that said positive have no line!?