Chest and back have been hurting my sternum is sore to the touch iv been to my doctor and she medically cleared me i have anxiety to what causes this?

Costochondritis: Costochondritis is inflammation of the junctions where the upper ribs join with the cartilage that holds them to the breastbone or sternum. The condition causes localized chest wall pain and tenderness that you can reproduce by pushing on the involved cartilage in the front of the rib cage. Costochondritis is a relatively harmless condition and usually goes away without treatment. Shiel et al.