I tend to agree with Ken. I also had costochondritis that was pain in rib cartiledges and once I had to be admitted to a heart hospital overnight for observation. I was OK. But an evaluation of heart was done before I was discharged. You may go to Dr . and go for TMT ECG.
The pain could be associated with skeletal or cartilage as part of the rib cage...that would be most likely if you change sitting or standing position and take a deep breath. More likely the problem is associated with the respiratory system caused by pulmonary thrombosis (clot) and/or lung embolism. That would be the worst case scenario...there are many causes for your symptoms and you should have an exam to evaluate and dismiss any serious heart and/or respiratory disorder.
Hope this helps. Take care,
Ken.