Could chronic cough be due to thyroid condition?

[Siegie]

I'm 41 w/ hx of breast cx (dx 39 yrs, IDC & DCIS, stage I, chemo no rads). My original CT scan after dx (9/07) showed no nodules on thyroid or in lungs. My last 3 scans showed lung nodule but it appears to be stable. Prior to starting chemo I had an enlarged lymph node on my left side of neck. It eventually decreased in size but I can still feel it. I  convinced my onc. to scan my neck when they did lungs April '09. That showed nothing on lymph (although still palpable) but showed small (4mm) thyroid nodule. No big deal lung & thyroid nodules apparently common. I've had a chroinc dry cough since Aug. '08 -every day! I've seen a GI (endo-neg), pulmonolgist (bronch, neg-asthma test), & allergist. I've taken tesslon pearle, singulair, adavair, allegra, chlorotrimeton, predisone, prilosec, zantac, prevacid of which none helped. Tussinex works for about 24 hrs. I'm now taking a ppi (either nexium, prevacid, or kephalex) 2x/day - 6wks now. Still coughing. Can feel the nodule on the front of my throat...not noticed before but perhaps it's been there all along.?? It is a little tender to touch. Had my TSH tested by gen pract. - normal 1.75. Should I request further testing on thyroid and could my cough be due to thyroid nodule? (Fam cancer History: mom-colon, mdad-bladder/prostate/melanoma, several great aunts & distant cousins w/ breast cx, 2nd cousin w/ thyroid cx (shown up as stuma ovarii), other on mom's side cx's (lung, melanoma, colon, bladder, stomach) that we're aware of. Dad - prostate/GIST, thyroid problems w/ his sister & mom - benign). Mom has seen geneticist - says her cx not due to predisoposition gene. I don't want to seem like a hypochondriac but my cough is disrupting to say the least & costly. The ppi treatment is very expensive for me in addition to my other meds. Should I wait longer to give ppi's a chance (dr. said could take 2 months) or look further into thyroid. Doctors have not pursued this avenue at all. I see my onc next in Jan. Thank you.