There is no medicine or exercise to correct myopia. At your age you must use properly tested glasses regularly, only this can prevent your worsening. Refractive surgeries are quite safe . Have high protein diet with fresh fruits and vegetables. Don't use mobile unnecessarily, Keep the book /laptop at least 18 to 20 inches from your eyes . Sit in a position so that the light comes from back and left. Don't sit facing a/c,table fan or blower.