i just want to second what someone else mentioned. If your eating something like corn that your system doesn't digest, its best to not eat it, and things related to it. like popcorn... i also try to avoid stuff with high fructose corn syrup too, as its corn based too.
I've talked to docs about this, and get the so, don't worry about that.
For some people milk can cause a lot of mucus, not only in your sinus area but thru out the body, and digestive tract and cause some bloating and other issues.
You may want to try to do some trials, like with out certain potential problem causers. Or, if you happen to eat a ton of cheese one week because you bought string cheese, and things are worse... well maybe something to cut back on, and if able to eliminate it for a couple weeks and see if your symptoms feel better.
A friend had said that some of problems were probably from dairy. I have never drank milk, just don't like it, etc. Well, what i was eating was cheese, and i did protein bars or shakes before i would hurry to the gym, and there was whey-which is dairy. So, i went to a holistic person who said to eliminate dairy. So, i tried it took a couple months to rid of most of it. I did it one food item at a time.
I of the mind that if you change to much at one time, you will fail miserably and go back to it if i try cold turkey for many things at once. You have to adjust to things in your own pace. So, like i gave up the obvious cheese first. I did that for a few weeks. Just that on my dinners was rough. The worst part was the first few days, i don't really miss it much now. Find a replacement flavor, like mustard, ketchup, something tummy friendly.
Then i started to notice that once the flagrant dairy was out, my symptoms got better. Then i started to notice after i ate certain things i got stuffy. Well, i thought i'd looked thru labels, but then thats when i found the protein powder and bars i was eating had whey in them = milk.
It is hard when i eat out. However the only time i eat out is maybe 1x a week, and mostly its every other week. Then if i eat small amounts i'm ok, but can tell the next few days. I still forget to ask no cheese on things, besides a ton of other issues.
Good luck