Hello Mr Graham
You have not mentioned about fever status, any change in body weight and whether cough associated with sputum. As it is a chronic cough
, you need to be evaluated for Pulmonary tuberculosis
by Chest X-ray, Sputum analysis and several blood tests. If everything normal then chronic cough could be due to bronchitis
which is common in chronic smokers. Try to quit smoking if your smoker. Backache is usually seen with pleuristis or could be a muscle pain
. I suggest you to first get done evaluation for tuberculosis.