So much pain and it's not even labor yet...help! Repost from 3rd tri and natural birth board..

Hey everyone!  I'm in desperate need of some tips and advice here.  I've had an amazing pregnancy...nothing really to complain about.  Then I hit 38 weeks..I had a few rough days that weekend...contractions for a whole, some pain..but everything went away for the most part and it was nothing I couldn't handle.  However, I took a walk this past Sunday with my husband and since then I've had some pretty rough back pain...off and on, but for the most part on.  I got excited of course, thinking it meant things were moving along...I'd have contractions if I walked, but as soon as I relax, they go away.  The pain pretty much starts in my middle back on my right side and radiates down into the top of my butt and around to my right hip and groin.  Monday it took me 2 hrs to do what normally takes me an hour at the grocery and by the end I was shaking!  And I'm so not one to complain...like I said, this pregnancy was pretty much amazing!  Up until today I've been able to kind of keep the pain bearable by doing yoga and keeping thermal patches and ice/heat packs on my back.  Today however, nothing will get rid of it.  I can't sit, stand or lay down comfortably...I've been trying to sleep for almost 3 hrs now, with no luck.  No position gives me any relief, heating pad and all.  Anyone else deal with this or have any ideas?  Thanks so much, I know this is super long...I just don't know what else to do or how much longer I can do this!