[Gargamel]

Those aren't flu symptoms. Flu symptoms are Vomiting, Diarrhea, weakness. You guys are describing Cold symptoms. And because you are getting them at regular interval during seasonal changes, it's most likely a seasonal allergy. It could be a cold, but it sounds more like allergies. It doesn't have to be a pollen from plants, it could be something as simple as a seasonal mold spore release, or dog dander from shedding with the weather change.