How To Treat Shoulder Pain Radiating To Neck And Chest?

hello doctor.my name is mina.55 years old female.weight 55 kg,height 158 cm.i am having eft shoulder pain from nearly 5-6 month.i am not able to do any heavy task with my left hand.also can not move up my arm.the pain does not radiate to chest or neck.but whole arm feel stiff.what should i do?