Husband poorly waiting on ct scan.. possibly lung cancer???

My husband has had a terrible cough for the last 3months. His been breathless and bringing up lots of mucus. His had 3 different anti biotics with very little relief. His had 2 sputum tests which have came back clear. His had bloods taken which came back fine. He then had a chest x-ray which showed a shadow on his lung. They first said it's pneumonia and gave him the third course of antibiotics. His still no better so his been refered for a ct scan in the cancer 2 week referal although our Dr said "not to worry it's just a precaution" and said it's unlikely to be cancer.  we are worried sick. His 47 years old and we have 2 small children. Anyone could help us shed some light???