Hi,
Welcome to the ehealthforum and I am really glad to help you out.
The typical site which you have mentioned along with a history of smoking suggests acid reflux from smoking. First of all stop smoking and avoid eating any junk food or oily, spicy food.
Take a healthy,balanced and nutritious diet consisting more of fruits, salads, soups and raw vegetables(after proper washing).Also increase the protein content in your diet instead of carbohydrates and fats.
An advice from a dietician will be helpful. Take some OTC antacid like Mylanta. If the symptoms persist then please consult a physician and get a CT scan lungs done.
I sincerely hope that helps. Take care.