6 year shoulder injury

Need help with a 6 year shoulder injury

I injured my rear deltoid doing rear deltoid flys when i was 16, i was a boxer and also weight lifting. The rear delt pain was intense as i didnt stop training for 6 months after the injury. It has been constitent pain for now 6 years and cannot go to the gym. I had pain in my what i believe my rear delt, teres minir and major and when it flares up my shoulder drops forward and turns inwards and also feels as if my pec and curled up in my chest and i cannot do any shoulder exercise without intense pain and weakness. I have seen 2 orthapedic surgeons, around 10 physios, and 3 osteopaths. I have also had 2 MRI. On the shoulder and xrays. And shows nothing...... the pain is intense if i reach out in front with any weight. And my rear delt and the little muscles below my rear delt feel like there rubbing and popping and clicking all the time. I have been tjeough shoulder rehab about 15 times over the past 6 years and still the pain is consistent and i have never been able to train again. Can someone please advise me