Braxton hicks? Start of labor?

Courtney
I've had horrible cramping all day. I can't lay down to nap without the pain waking me up. Lower back is killing me I don't think it's anything as far as labor yet..I haven't lost my plug nor has my water broke. I feel like a can't time anything because it's one big cramp..any advice from anyone would help. I'm 39 weeks 1 day.