Right, here comes the pontificationizing...
The reason for my suggestion that mrcharly see his quack was to make sure that it is nothing serious. Serious like an infection, cancer or something else.
Now, I know backpain is potentially life-changing (a fall off a rockface, a period of not moving my legs right, emergency surgery and now a drop foot have seen to it that, boy, I know). What backpain in itself isn't, is threatening to anyone's life or function. Opinions and behaviour related to the pain can and do, however, destroy lives. By this I do not mean it's all in the mind. What is true, though, is that attaching undue significance to sensations in the back can lead to a vicious cycle of fear, avoidance, stiffening up, de-conditioning and more pain.
In my professional life (pain clinics) I see many patients who have been round this cycle a few times. Injections, scans, nerve blocks, surgery all have a pretty poor record in my experience and actually little by way of evidence to support them. All the evidence lies with a positive attitude, continuation of gentle movement while it hurts, structured programmes of rehabilitation (pilates is as good as anything) and paracetamol and ibuprofen. Spasms can in the short-ish term be relieved by Diazepam, at the cost of drowsiness, and by acupuncture or chiropractic, at the cost of some dosh and time.
Chasing an anatomical diagnosis by means of scans is likely to do more harm than good. Scans done on people with no back symptoms at all routinely show a third to half to have impresive-looking "abnormalities". So if someone sees something on a scan, does it mean owt? Or nowt?
Mrcharly, you're clearly already doing most of the right things. Now just wait - it'll go.
[/quack-quack mode]