Hi,
what you have experienced must be quite frustrating.
Exercise programmes are individually designed, therefore, someone needs to assess you (subjective = what are you symptoms and your goals; and objective = measuring muscle strength, control, cardiovascular aspects, balance, etc.) and can then design an exercise programme for you. This programme will then be tested and adjusted until it sits well with you and reviewed on a regular basis to check for progressions.
The people who do this are Physiotherapists, Personal Trainers and Exercise Physiologists.
If you are concerned about an underlying pathology and would like that investigated during the assessment- see a physio.
If you think you are generally fine and would like to improve your shoulders in general - choose any of the above.
Hope you are able to find a solution,
kind regards,
Fyzzio