It's the chest wall, when i breathe in it hurts,?

See your doctor: have your doctor check your chest, and hear you breathe, so s/he can listen to your breath sounds, and make sure your lungs are okay. If they are, then s/he'll check your ribs, to make sure that your ribs aren't inflamed. If you notice it more upon breathing in or only when exhaling out, it's pointing to ribs or musculoskeletal issues. Get it checked out soon.

Diaphragm fatigue?: When there is pain with inspiration there are several things that can cause this - diaphragm muscle fatigue from overuse with respiratory illnesses such as asthma or bronchiolitis, rib bruise or fracture, chest wall inflammation =costochondritis, pneumonia, lung contusion in a car accident, the list goes on