There should be a reason for your lung to collapse.
What came out through the chest tube
? was it air ,fluid or pus ?
Has your lung expanded after the tube placement?
Has the tube been removed?
Does the CT scan
show anything that is obstructing the bronchus
( branch of windpipe supplying air to lung ).
Lung that has been collapsed for around 5 months may take time to expand completely.
Also prolonged collapse can cause your ribs to be crowded , hindering expansion.
bands have been formed in the covering of lung it can also prevent proper expansion