My name is Nesim and I will try to explain to you why your back hurts so much:
Upper and Middle back pain may be caused by: Overuse, Muscle Strain or Injury to the muscles, ligaments and discs that support your spine.
Also even poor posture could cause this pain. You need to walk and sit straight.
Pressure on the spinal nerves from certain problems such as herniated disc.
Those could all be the causes of why your back hurts so much,
But if it's really that tough I would go and visit my doctor.
Hope this answers your question, and if it does make sure to leave a like so more people can read it through and perhaps resolve the same problem.