cramping in back

sunsurfer655

Hi ladies!  I am normally just a lurker, but I was hoping you could help answer a question.  I'll be 38 weeks tomorrow and I've been having some tightening/cramping in my back since late morning.  It doesn't spread around to the front of my belly, it's mostly just in my lower and middle back.  Is this just normal pregnancy discomfort?  It's just throwing me that it feels like it's coming in waves, it's not a normal constant pain and I'm not feeling it in my stomach at all.  Thanks for your help!