Early labor?

I'm 40w5d and since last night I've had period like cramping. I've noticed that I usually get this when my baby is moving her head a lot (she's as far down in my pelvis as she can go before labor.) she's been super active so I don't if that's what's causing it. When I have Braxton hicks my stomach gets rock hard but that's not really happening. The cramps are coming and going and they have gotten more painful, the discomfort radiates through my upper thighs. The pain is staying low instead of moving upward.