What Causes Pressure Or Congestion On Upper Chest While Having Dry Cough?

I have had a feeling of congestion or pressure on my upper chest for 4 weeks. The doctor sent me for a chest xray, an ECG and blood work and nothing found. I can take deep breaths with no pain in my lungs. I have a dry cough with no sputum. Can you give me any idea of what this possibly could be? My doctor seems to be stumped. Should I be asking for a CT scan? I am worrying about lung cancer, I am not a smoker but have been around second hand cigarette smoker a lot of my life.