I'm a veteran, not a doctor, (but I did stay at a Holiday Inn Express).
I have a minor intolerance to PG. I can't handle more than 30%. When I vaped 50/50, I was getting throat irritation and a tightening of my throat and chest. Not a lot of mucous, but sinus draining and irritation. It didn't start right away, but after a couple months. I cut the PG completely out and it all cleared up. I gradually worked my way back up to 30% where I'm staying now.
Since you've already seen a doctor and nothing is medically wrong, I'd say you might want to eliminate the PG and see what happens. You can add a little back in at a time if it clears back up so that you find your tolerance level. 100%VG is o.k, but not optimal. It has it's drawbacks. Full blown PG allergies are very rare. Some degree of intolerance not so much.