You can question the need for antibiotics...
Antibiotics are useful drugs; therefore it has been abused and used inappropriately. I appreciate the fact that you always consult a doctor before using antibiotics. You can question the need to use antibiotics the next time you have symptoms. If the cause is viral (which is often the cause), you don't need antibiotics.
As far as the second question is concerned, supplements can be taken. But remember, the supplements are only supportive treatment. You will need consume healthy mix of diet along with exercises with it.
Genetic frame work can make you sensitive/allergic to external environment. Therefore using precautions whenever needed makes sense. You can follow certain life style changes strictly such as avoiding cold
and refrigerated food products. Besides as your symptoms are predominantly nasal congestion
, it would be worthwhile to see an ENT surgeon to rule out other treatable conditions such as a sinus
I understand the recurring conditions are troubling. The answer may or may not be only "sensitivity". A thorough check up with right specialist is my suggestion to you.
Hope this helps.