I Have This Very Uncomfortable Pain On My Left Shoulder

I have this very uncomfortable pain on my left shoulder blade for years (15yrs)and no matter what I do,it won't go away. I've tried acupuncture,massages,cold and hot therapy,tried yoga,sleeping differently,seen several doctors and they all say I'm fine. I know it's not in my head but I just feel that I was never properly diagnosed bc I don't have health insurance ....