I have pain that comes and goes based on the position I am in or how I use my arms. I there is lifting or not. The pain today is in the center of my chest but more to the right just kinda into the right breast but feels like a muscle or pulled cartilage.If I press on the area in a certain spot the pain comes. No coughing or fever. I have been going thru physical therapy for my right leg and this includes exercise that I am learning how to do at home. Some of them include core work and don t know if I did something wrong with these.