Could Severe Pain In Arm Be Due To Shoulder Sprain?

Hello Dr. Joshi.I am 31 yrs of age.few days ago during my work on the ship,while i was unloading a heavy bag of approx. 55 kgs from a height above my head, i stretched out my hand and suffered severe pain.x-ray report shows no bone damage.The doctor says it could be a moderate or severe shoulder sprain.I am still suffering pain and weekness all around the shoulder,at the back just bellow neck,and around the biceps.My both hands fingers and around the wrist bocomes numb at night. i cant even carry a bottle of water for more then a 30 seconds,i fill weekness. can u suggest therapy and exactly how long it will take to recover and return back to work.