Had 3 chest x-rays over 3 months due to cough and tight chest. respitory specialist is not concerned about anything sinister. hyper anxious. cancer?

Cough: Consult your internist and radiologist on what the cause is, if it was cancer they would have pursued more investigations normally.

Probably not: It is very unlikely that this would be cancer because you are young and a never-smoker. If your cough and chest tightness are not improving, ask your lung specialist if a chest ct would be advised.