Why those my back hurts whenever am under a fan?

Cold: Your muscles may be tensing up due to coolness caused by a fan. Wish you good health! - Have a diet rich in fresh vegetables, fruits, whole grains, milk and milk products, nuts, beans, legumes, lentils and small amounts of lean meats. Avoid saturated fats. Drink enough water daily, so that your urine is mostly colorless. Exercise at least 150 minutes/week and increase the intensity of exercise gradually. Do not use tobacco, alcohol, weed or street drugs in any form. Practice safe sex, if you have sex.

Possible : Exposing you back to the air directive of a fan can expose the large muscle of back and sides. This cooling effect on the muscles can trigger spasms which results in back pain. These muscle spasm are due to overuse or extended use of the fibers. Your core can be weak or muscles injured. You need to stretch and strengthen to help minimize these incidents. Physical therapy would help.