this is a hard one to do, i wish i could give my details to you to come for a few sessions to help sort it out but yeah,
the limited advice i can give you is to go see a reel good BIO / PHYSIO to help sort it out before you consider the worst (doing surgery) and the chances of it being successful is not a lot.
other advice i can give is to do following exercises:
shoulder flexion 5 reps
lateral raises (body weight) 5 reps
arm across chest stretch 20 second hold
door frame pec stretch 20 second hold
external rotation 5 reps
internal rotation 5 reps
remember i can give you a few exercises but i cant track your progression and look at your form(ROM) or do a proper posture analysis to see what else is contributing to it and if there is any other problems.
its vital that you do the above prescribed exercises at least 3 times a day or 6 times a day, i know this
sound a lot but to correct something like this isn't done with one mini workout a day (ask any bio)
lets try to sort your shoulder out now before it becomes more severe or is unable to be rehabilitated, so please do the exercises till you find a good bio or physio that can help with your shoulder with a more hand on approach.
let me know on the progression and any other problems like exercise aggravation so we can adjust the exercises.
Biokinetic