im a 19 year old female and since july of last year i have been having pain in my left shoulder an

im a 19 year old female and since july of last year i have been having pain in my left shoulder and upper arm(this is my dominant arm),its like a sharp and dull pain,things like stirring liquids,holding heavy things above my head or even just holding heavy things and pushing or pulling heavy objects will bring this pain on through out the day,but it always comes in the afternoon/night even if im not doing anything,sometimes throughout the day it feels like its locking in place,i can feel its click when i move it to get it out of the locking position iv had blood tests,steroid injections,anti inflammatories(x2),antibiotics,iv rested it in a sling for 2 weeks,exercised it daily,had a nerve test done for Carpal Tunnel Syndrome all tests came back negitive my docter still has no idea what this may be,i was just wondering if anyone might have had something like this and might have an idea what it may be i also have neurofibroma,i was kinda thinking it could be a lump inside my arm causing all the pain,or is it something else any help to helping me find out what this might be would be very well appreciated i have an appointment with the orthopaedic surgeon,but it aint for 8 months thanks in advance