Trapped nerve?

Really need some advice please. I am a 40 year old female... In February after doing a strenous walk for charity, I woke up the next morning with what i'd describe as a cricked neck. Could not turn without pain and was stiff, then I started getting pains in the back left shoulderblade. This then started to radiate all down my left arm and into fingers. I saw my doctor who said it sounded like a trapped nerve but was not sure. Was given painkillers and anti inflamatorys. I cannot take codine as have a bad reaction to it, so was getting no relief from the painkillers at all ibroprufen, After 6 weeks of bad pain it finally went away as I was told I would not be reffered for help until after 6 weeks.
Last Monday I woke up to find that this was back again, I had been doing some heavy lifting the weekend before.
The pain this time didn't come on in stages as before but I have the neck, shoulder, and arm pain back intensly.
Again visited my doctor last week and they asked what i'd like done? I said i have no idea i'd just like to have a diagnosis then possibly treat the problem rather than be fobbed off with pills again. I have been reffered for physio but the waiting time will be weeks, Would physio help this problem or could it make it worse as I have no diagnosis?

Any suggestions please?