You're symptoms are identical to the cough I have (among various other multiple problems)- which seems to finally have a diagnosis , which I've been seeking 2yrs. The coughing is like the end result of it all - and just like you , no smoking , no drinking . The cough has no seasonal changes as well ; and I can relate to KatEyes symptoms as well . Now they think I have coccioidomycosis .You will not find out much in your average medical symptom book ; nor did I see anything indepth online . It is relatively rare since 60% who get this have little or no symptoms .If you go to the reference section of your local library , much more can be learned .If you are getting nowhere with all of the testing you undergo , you might see an infectious disease specialist .Never in my wildest dreams did I ever think I would go through 2 yrs of not knowing what is wrong or what to do about it. Now that they think they know what is wrong..I wait for yet another doctor (infectious disease) making this probably around a dozen different specialists.If lesions begin to surface in xrays & CTS , etc. it could be an infectious disease. Good luck.
I have had different lung problems over the years. Recently my docs had been checking my heart every few years,and finally figured out my increasing shortness of breath on exertion was coming from my lungs, although I'd been x-rayed every year. After several years my lung volumes tested out decreased and inflammation showed on the x-rays. I have interstitial lung disease. I'm not saying you have that, just that sometimes things are not evident, but it doesn't mean nothing is going on.
In prior years I had reactive airways after an episode of inhaling toxic fumes. While I coughed all the time, certain smells would trigger asthma-like attacks. There wasn't anything that showed on tests, just the incessant coughing. I had to de-scent my environment of chemicals, cleaners, detergents, hygiene items, etc. You might try doing that for a period of time and see if there's an improvement when at home.
I know how aggravating a cough can be. Hope you find answers soon.
There are certain BP meds that can cause a bad cough, but you don't mention being on those.