I Have Had A Horrible Cough Since Late June, 2015.

I have had a horrible cough since late June, 2015. I've seen my PCP twice, 2 different lung care specialists 3 times, and an urgent care doctor twice since September. Two chest x-rays were negative, lungs clear. Cough begins with tickle (always on the left side of throat just below collar bone). Then my left eye gets slimy and my left nostril drips with a clear liquid. Doesn't matter whether I'm up or laying down. Coughing attacks come on suddenly and can be very embarrassing when in public. Can't control it. I've taken Amoxicillin 500mg for 5 days, then Levaquin 500mg for 7 days, then a Rochephin shot, along with OTC meds and antihistamines, but nothing controls it. I have a 1.4cm cystic nodule on L lobe of thyroid. Fine Needle Biopsy revealed blood only and was nondiagnostic. I am due a followup thyroid scan, but can't get it one until I can lay on my back long enough not to cough. I wake up 4 or 5 times during the night coughing. Cough never reaches deep enough to satisfy the sensation. What do you suggest? I am 68 years old, do not have GERD; I do have asthma and occasionally bouts of bronchitis. Could my thyroid cyst be associated with the cough since medications haven't relieved the symptom? I have been referred to an ENT and a Pulmonologist. I have seen 2 pulmonologists and they did nothing to help.