I had similar many years ago, went to Docs who sent me to an inhouse chiropractor i think he was. Assessed me and gave me some very simple stretches to do. The relief was almost instant. Like you, i hadn't done anything that i knew of to hurt my back. He explained as we get older some people just need to work a bit of excersise to keep your back in good shape. I still do them occasionally when i remember, just stretches really similar to what anyone would do to warm up before doing gym excersises etc.. They're good for me anyway. I'd go to the Doctors if i was you, you shouldn't be needing a back support unless you have severley damaged your back i would of thought.