hope you've called your doc and all is well with you. if you're concerned and the pain's persistant, please go in and get yourself examined, even if you have to fight your doctor tooth and nail. some things you've said concern me due to the experience of 'a friend of a friend' who was also thirty-seven weeks. i'm not trying to alarm you or cause you undue stress, and as such, won't relate her experience unless somebody asks.
what you've described kind of reminds me of my experience with back labor, which was the most agonizing and intense pain i've ever felt (and lasted wayyy too long!#!).
for me, HEAT was the one thing that seemed to make it bearable - take hot showers with the water beating on your back, or soak in your tub if it's an option, or try a heating pad (i was so desperate for a heating pad that i had hubby tear open the emergency kit we store in the van, haha). back to tubs, if yours is a decent size, make it your best friend -- the water and warmth will alleviate some of the pressure and the pain, especially if you're lucky enough to have a large one where you can assume different positions, like on your hands and knees (which i hear works wonders). also, laying in bed and elevating your hips might help (have them and your lower back slanting down and towards you). the nurses at the hospital suggested leaning over a bed, putting hands flat on the mattress and rocking/swaying the hips and walking too, but neither option really worked for me.
whatever the case, good luck to you and i hope you get some relief!