Taking a fecal sample to a vet is a really good idea. It's relatively inexpensive and it's a good starting point for diagnosis. I would also suggest that it's not something in the air but perhaps a bacteria carried on your shoes. In vet offices where I've worked anyone that has been working with animals that are contagious have to walk through a disinfectant for their shoes before leaving the area. I hope the worst is behind you and I'm sorry to hear about the trouble you are having.