Scan, doesn't particually sound like a bad GP.
I'm making a few assumptions here, (duration of symptoms, any "danger" symptoms etc), but at this stage, it would probably not be prudent to send you for a scan.
There are several reasons for this:
a) It is unlikely to make a difference to your outcome (at this stage).
b) Sending everyone who complains of back pain (about 40% of the population) for a scan/x-ray would cause more harm than good. Can't remember the exact numbers, but I think about 200 (UK) cancer deaths per year are related to medical imaging - particually important in back pain management - a lumbar x-ray is about the equivalent to 50 chest x-rays.
c) Its not always a particually helpful examination. (Lots of scans are "normal" but the pain persists, some "healthy" backs show radiological abdnormalities.
Have you tried strengthening the structures around the area, swimming may be useful. Also keep those abs trim, as sloppy tummy muscles can cause problems. Also, try and keep your weight down.
Hope the info's useful, if you feel "fobbed off" by your GP, go and tell him/her.
ps try and get hold of a copy of your firms "lifting and handling policy." Every large company is meant to have one. Ours is gathering dust in the managers office............ouch! anyone got any brufen !