FFN negative

I’m 33wks1d… I’m high risk for preterm delivery . Today had my FFN and it came back negative . However my NST showed uterine irritated and contractions which I can feel that go into my back and my whole stomach hurts.. also I get the feeling of needing to have a bowel movement as well. Has anyone had experience where FFN was negative and still ended up going into labor ? I just feel myself. My OB hasn’t checked me either to see if I’m dilating Or effaced.