Coughing again

Hi all,
I don't like to read long posts so I'll give some background and cut to the topic.
Diagnosed June 2010 NHL-B 1st stage, 8lb lump in my chest and water under my lungs caused allot of coughing.
I completed 6 R-CHOP chemo's and 20 radiations late November, about a month age. The lump was reduced and pet and cat scans look good.It took about 3 weeks to feel some what normal and then suddenly in the last 2 weeks I started coughing again.
Not coughing up stuff or a cold or something like that. This is lung irritation like the mass pressing against my lungs of the fluid under my lungs. My wife is worried, she wants me to take cough medication but I know it won't help this is something else.
So here is the question...anyone else know what I'm talking about? I wasn't coughing during Chemo or radiation it just started again.
OK I said the post wouldn't be long so if your still with me sorry for that.
Thankx in advance for any comments.
Steve