wOw .. your home humidity is very low. I have 5 tropical fish tanks in my bedroom for the past three years. Prior to having them there the humidity was low, wake up with congestion etc. Those symptoms have disappeared and I went 2 1/2 years without even a cold .. until I was scheduled to visit my daughter in S.C. .. yep caught a cold the week before (but it was very mild and gone just before leaving :0)
I suspect the reason isn't too low .. or too high but your constant daily change from one to the other. Your body is in constant adjustment mode and why you get sick easier. I would up the humidity in your home.