It is common condition seen by Physio.
1. control the symptoms-use anti-inflammatory gel every night before go to sleep can help if do have inflammation happening, and maybe some pain control to help you go to exercises.
2. correct contributing factors-forward shoulder, poor scapular control during movement, stiff thoracic spine, which can treated by exercises and mobilisation
3. Eccentric exercises: use pulley to low down you arm slowly, it is an exercises with pain, and will take long period of time. would be better to have someone instruct you.
Would suggest you to see physio to manage it.