You are describing pleural effusion where fluid accumulates between the pleural space and the lung. There are many reasons for this to happen besides cancer such as infection (pneumonia, TB...), heart/kidney disease, pulmonary embolisms, autoimmune disease (lupus), The doctors need to figure out why this is happening to you...what have they told you and what tests have they run on you?
Sunny
fyi,someone else on the site has a question about fluid build up in lungs.Question did the drs ever tell you this could cause death or a suffacation problem?