Easily get cold / sore throat, why??

Hi everyone, as  the title says, I get my throat a bit inflamed pretty easily; it itches, feels swollen, sometimes even hurts (almost always on the sides, close or at the back of the tonsils). While most others can wear short sleeved clothes, get a bit rain-washed, drink cold stuff when it's not hot outside, etc, those are almost sure cold triggers for me. Only in summer (20-28°C or hotter) can I do all those things care free.

Past related medical history includes several tonsillitis episodes in a year (1998, after which their size decreased by about half, and I started having mild ones about 1-2 per year). My right nostril is slightly closed , so I have to blow my nose a few times every day to decongest it (funnily, my MD said it was fine and didn't need surgery, anything). I have 3 mercury/silver tooth fillings, which could be increasing toxicity levels inside my throat. They are rather small, though. Something else, probably very important, I get runny nose right after waking up and for the following 2-3 hs in very (90%+) humid places. I used to live in such a place and it ended up being absolutely unbearable, I reckon my mouth/nose/ear tissues could have gotten chronically sensitive bc of that. Finally, I'm 39 years old, male, quite fit (work out almost every day since I'm 12), no other major ailments whatsoever. No medicament/food allergies as far as i know.

Please help. I reckon I may have a chronic infection in the throat that for the most part goes unnoticed, and that's why I get cold symptoms so quickly after being exposed to cold. Any comments or observations are very, very welcome.

Cheers