Tight chest when breath lung and heart tests clear it's near the sternum can make me cough sometimes what is it been 3 months now ?

R/O asthma: Have you had a PFT study (breathing test) to rule out asthma? Your symptoms in a 17 year old are most likely due to asthma. And get a chest x-ray if you haven't already. See a pulmonologist (asthma doc).

Asthma: can make breathing difficult and trigger coughing, wheezing and tight chest. See your doctor for spirometry, provocative testing and peak flow test to support the diagnosis. Take care.