Welcome at HCM.
I have read your question .It looks that you are having pain on taking your arm towards your back as well as on elevation.
Your details shows that you may have either impingement syndrome
of your shoulder.This can be better diagnosed by clinical examination from a orthopedic doctor & having a MRI
Your doctor may give you relief by giving intra articular steroids
& some good analgesics.
Some exercises are also helpful in relieving these problems ,for this you may take help of your physiotherapist.
Hope this all will help you.
Wish you a happy & healthy life.