Chesty cough after having flu over5 weeks ago , cough a lot during night , feel as if lungs are congested , also having night sweats , otherwise well ?

Fevers?: It sounds like you may have a reactive airway. This can happen after having a viral upper respiratory infection. Please followup with you primary doctor for a chest xray to rule out pneumonia or tuberculosis. If xray is clear or shows bronchitis, your primary doctor may prescribe prednisone, a steroid.

Reactive airways..??: After full recovery from flu - either other virus or environmental bronchi irritation leading to congestion and sometime bronchospasm - worse at night, or with exertion. Night sweats may also indicate some underlined infection - possibly check with doc. if appropriate to do CXR( chest X ray).