Hi there!
Well, without a clinical evaluation it would be difficult to determine the cause of your shoulder pain. Possibilities that may need to be considered include inflammations, degenerations, capsulitis, bursitis, tendonitis, injuries/ tears, arthritis, spinal/ neuro-muscular causes, muscle/ ligament/ tendon tears/ injuries, fractures, growths/ masses, ischemia, micronutrient deficiencies etc. I would suggest getting this evaluated by an orthopedician for an accurate diagnosis and appropriate management.
Hope this is helpful.
Take care!
A detailed clinical evaluation of your condition is needed to arrive at a diagnosis. Possible conditions include shoulder subluxation, muscle strain, myofascial pain syndrome, rotator cuff problems etc.
We need to address the cause of the pain so that slumping will be corrected. Moreover, prolonged slumping can also cause other problems related to postural fault.
I hope this information will help you.