Slipped Disc
Having injured my back in the RAF and having had 4 weeks of misdiagnosed physio. Resulting in the physioterrorist pushing on my later discovered pair of permeated discs once a day until tears came out. I would definately push for getting a MRI. Especially if the pain you experience radiates elsewhere. When my back hurt I got pain down one leg into my toes. Even when I suggested that the two pains (back and nerve pain in leg) were associated the RAF doctors insisted they weren't. Long story short- if I had gone to see a specialist who knew what they were talking about and got an MRI done I would have had the surgery I needed earlier and most likely wouldn't still have niggling pain some 5 years on.
Good luck getting it sorted! PS its never caused me any problems getting a class 1 and a civvie job