Yes, in no way was it the yeast itself. I'm glad doctors are still indiscriminately passing out anti-biotics despite the potential repercussions.
I would try to think of some other change that has occured in you and your roommate's life... change of living situation, new work/school environment, spending a lot of time in a car, taking up smoking(
). Does the cough increase/diminish when you go from one environment to another? It could be mold, allergens (change of seasons), or just some crazy virus that took hold. If it's a virus, it will go away on it's own. If mold due to water intrusion is highly suspect (drywall stained, flooring buckling, musty odor, etc.), you might consider getting your home evaluated by a reputable
firm. You can PM me for more info if you narrow it down to mold due to water intrusion.