Those sound like symptoms of a PG allergy to me (I have one). I vape 90% vg and 10% distilled water, to keep temperatures in my tank and coil down. Someone recently suggested PEG400 as a substitute for PG, as even with DW added, I'm a bit cloudier than I care for. It's working well so far (am using it cautiously still, to make sure I don't have a sensitivity) but so far, so good.
I'd start at 90VG/10DW for now, until you can get your hands on some PEG400 to try (if you so desire) because that will give your tanks less temperature/gunking issues, probably. I ordered mine from Amazon (a small quantity) but I will say that so far, I've been happy and will likely order in more bulk next time.
Good luck, if your coughing persists after you removed PG from the equation, I would say it might be good to see a doctor.
Best of luck,
Anna