what does early back labor feel like?

Jolene • Momma of a beautiful girl Kinsley Anne born Jan 18th 2016 and due with our 2nd girl Maddison Reece due May 15th 2017
So today I woke up hips were in a lot of pain, as usual. But now I'm having a constant, almost pinched nerve feeling radiating from my hip to mY butt like to my tailbone, it's super low. Only on my right side! And sometimes feel it run down thigh just barely.
Sometimes it gets a little worse feeling, but it's nothing I can really time because I have a constant pain, and then like every now and then a surge of even more pain. I've tried to change positions, I tried moving my hips around maybe if it was a little pinch nerve I could just move around a bit and get it loose, but I can't! 
38 +3 wks I have a posterior cervix, this is my 2nd I've carried low all pregnancy and she's pretty far down there. 
Anyone think it's just baby on a nerve? Or possible back labor?
Any help 

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