My son will be 6 next week. He also played the cough @ night, frequently sick w/congestion, albuterol, singulair, flonase, etc... game.
When he was 3, I insisted that we take him to an allergist who did a skin test and said he wasn't allergic to anything, but ordered a cocktail of medicines that effectively kept him off of antibiotics and reduced the number of incidents.
I was still unhappy with the amount of medication he was taking so I took him to a naturopath simply b/c I knew they would do what I wanted (blood test). I told her I was not interested in a large quantity of supplements. His test came back positive for a number of things including tree pollen, grass, & cat, but also significantly for egg, wheat & soy.
We took him off of egg permanently (including baked goods), but only avoid wheat & soy during allergy seasons. It has worked wonders and really helps him feel better all around. Also, he's taken some ownership and looks out for his food allergies himself. We still have flonase and albuterol for when he gets sick, but that is much less frequent (maybe 2 or 3 times a year vs. at least once a month).
Naturopaths can also muscle test instead of blood testing. Since you'll be paying out of pocket, it's less difficult to choose alternative medicine imo (since you're not getting it for free somewhere else).
I also give my son local raw honey and cod liver oil, as well as probiotics (chewable tablets essentially like the stuff in Activia).
Good luck!