Physiotherapy for shoulder pain?

I have been suffering from severe shoulder pain for the past few weeks. I'm not able to sleep at night because of this pain. Also, I can't go for a long drive as I feel shoulder discomfort after driving for an hour. I don't know what has happened to me all of a sudden. I don't remember injuring my shoulder nor had any fall or trauma to my shoulder. My mom is compelling me to go for shoulder pain treatment from a nearby physiotherapy centre in Mississauga. What might be the cause of this shoulder pain? Anyone here had this similar situation? What have you done to overcome this pain?

I would suggest doing some shoulder stretches.