Why have I been coughing for 2 months and short of breath?

[Lumpy2004]

I have had a bothersome cough since March 15, 2017 (so roughly 54 days). It started out with a few coughing episodes throughout the day and within the first week I felt like I was coughing every 3 minutes.  The coughing got worse at night and right when I woke up.  I have been to see the doctor 4 times.  I have been told it was a cold, I have been told it was GERD / acid reflux and I have been told it was bronchitis.  I have been on antibiotics and Prednisone twice. I was also given an albuterol inhaler and none of these things helped.  I have also been having difficultly taking in a deep breath and feel out of breath if I walk up steps.  Other than the coughing and shortness of breath I have no other symptoms. No sore throat and I have never coughed up any mucus or blood.  
    Some history: I am 48 years of age. I was always around second hand smoke as a child. As a teen I was a smoker and smoked for about 10 years less than a half a pack a day. I haven’t smoked in over 20 years.  For the last 7 years I have cleaned homes and have been in contact with large amounts of dust and chemicals such as bleach and windex.  I rarely ever got sick so this is either all catching up to me or something doctors can’t explain.  Please help.