Pregnancy test

Ok I've got this but I'm confused . I've never gotten a positive pregnancy test before . On the 5th morning I took a pregnancy test and I saw it as negative I left it in my cabinet and left. When I came back I saw 2 line. I assumed it was evaporated lines so I ignored it. The next day morning I was tempted to take another one and I got a faint line . And repeatedly I've been getting faint line positive with 3 different brands . And when I checked again on the 8th morning I got a negative. I still do have my breast tender symptoms, cramps and lower back pain. I feel like period symptoms. But what confuses me is is there such thing as false positive ? And what should I do . Someone please help me