What Causes Pain In Shoulder,neck And Elbow?

hi, ive had an aching/burning pain in my left shoulder/collarbone area/base of neck and down to my elbow for about 5weeks on and off now. i saw my gp over a week ago, and he thinks it could be coming from the shoulder joint and put me on anti-inflammatories and muscle relaxants. they havent really helped, so he's sending me for physiotherapy... could this be something serious or am i just worrying myself?