Welcome at HCM.
I have read your query.It looks from your details that most probably you are having a rotator cuff tear
or tendintis at your shoulder.
The rotator cuff is a anatomical covering of muscles at our shoulder .Tendinits is inflammation of lining of tendon.
You should do following to have relief in this-
-Give rest to your shoulder.
-Avoid lifting heavy weight.
-Take an anti inflammatory analgesic
-If possible consult to your orthopedic doctor & have a MRI
Hope this all will help you.
With best wishes.