Amniotic fluid

I am 3 days away from my due date, last night I had a gush of fluid come out of me and it was more mucus than anything so I went to get checked to see if it was my water and the stuff on my panty liner tested positive for amniotic fluid but then they did two other tests that tested negative. I’m only half a centimeter dilated and only have contractions every now and then. Why would the fluid on my panty liner test positive for amniotic fluid but the fluid inside me tested negative?