Stupid question but...

Okay mama's I am 36 weeks 5 days at my last appt doc said I'm totally effaced and almost 4 cm. For the last 2 hours I have had horrible pain in my lower back. I mean like how it feels when you get your period kinda pain. Now could this be labor? I've tried water and laying down... I've tried laying in different positions. The pain doesn't go away at all it just gets worse. I just feel so stupid asking because this is my 4th baby but I've never gone into labor naturally I've always been induced.