Shoulder pain can be complicated. Your RMT may need to do orthopedic testing in order to narrow down the culprit. Here are some excellent stretches to add to your self care. It is not easy to find a good set of these!
Squeezing your shoulder blades together (scapular retraction) is important to build the upper back strength you need for shoulder and neck support.
Rowing exercises are a great way to strengthen the rhomboid, middle and lower trapezius muscles, while chin ups or lat pull downs will strengthen latissimus dorsi, stabilizing your shoulder blades.
Neck, Shoulder & Upper Back Pain: Stretches and Exercises: