I am 28f.i am getting pain in back behind breast position in back. i am getting it everyday in the middle of sleep and by morning it is reducing. why?

Poor sleep position: Nocturnal pain could be benign as poor sleep position or problem with mattress or it could be a serious problem like a tumor/ spinal disease. Upper back pain is usually positional. This means it will get better or worse as body position changes. Change your mattress. Get a massage. See a chiropractor. take some anti-inflammatories.