Are you ok on days you do not have to work?
If the answer to the above question is yes - you need to change your work place for the symptoms to go away.
As you mention you must have already tried - antibiotics, steroid nasal sprays, saline nasal sprays, antihistaminic and antiallergic medications, steam inhalataion etc.
I think you should consult a doctor about this, talk to him/her in detail and see if you could change your work place. Ask your doctor to recommend it - that would help.
Do let us know how you are doing.
Hope this helps.