my joints SUCK

i don't understand how the slightest amount of repetitive movement can put my joints out for days. i just helped my friend dye her hair last night, reaching to the dye and then bringing it back to her head every few seconds made my shoulder start to twinge. only my right one? i was reaching with my left too when i switched sides. once i was finished i made sure to do some stretches and then she went home and i went to sleep hoping it would get better, but it got SO MUCH WORSE. now it hurts to prop myself up in bed, reach out in front of me, just resting it in the wrong way makes it burn. i hurts so bad to try and raise my arm above my head. i had to stop doing cashiering because of this (which pretty much ruined any chances of me getting a job again). i have no idea what it is. it is a part of eds? joint instability and subluxation? rotator cuff inflammation? if so why the hell is it getting this inflamed from an hour of slight movement? i say "slight" because my elbow was doing most of the bending and reaching?? my 22nd birthday was yesterday and of course i had to end it in pain.