I read your posting and the first thing that I thought of was, do you have any lower extremity pains and also do you a burning feeling while urinating. If so you should have a urinalysis to confirm this or rule it out whichever way it goes, but if not maybe you should consider setting up an appt. with a reputable chiropractor and having a consultation. Many people have reservations about them, but I've only had wonderful results from going to them. I hope everything gets better for you! 8-)
You should have an ultrasound done. Could be anything. even gallstones. The stomach nerves are closely related to the back muscles and nerves so sometimes it may seem the pain is in your back, it may be coming from your stomach and radiating to your back.
Can you massage the area and the pain goes away, then comes back or can you not pinpoint it at all?
See a Doctor to rule out anything serious.
it just might be something with your kidneys.have your doc do a urine culture and maybe some blood tests.good luck!