hmm I have the opposite. The itch, but no discharge.
I think it still can be a yeast infection though.
As for it only happening at work, is the environment different to your home - in terms of temperature etc? Do you have wierd chair coverings?
Maybe that is having an effect. But to be honest..I don't know.
It is possible that that is "just the way you are". I thought I had a yeast infection ages ago because of a wierd discharge, and had some swabs done etc, and I was told all was ok, and it was just "me".