I'd test again if the nurse thinks its a false negative (might have been too early in germ cycle)
Whooping cough is extremely contagious, so if you do have it, you and your co-workers would probably be better if you stayed home.
Regarding the cough: vaporizer, Vicks, eucalyptus oil in burner all can help with breathing. My mum used to give us a 1-2-3 mix (used for croup as well)
3 parts water, 2 parts white vinegar and 1 part methylated spirits. (I used a 1/2 cup measure I think to get a good amount.) It stinks - which I think may be part of the 'cure'! We soak teatowels and put it around the kids' throats like a scarf till they calm down and breathe more normally.

I hope you are both feeling better soon.