I myself am PG sensitive. However, I figured this out with the help of my doctor. My hunch is it may be an ingredient or flavoring you are sensitive to, and it's a known issue that some folks with lung issues or asthma find too much VG to cause a "heavy" sensation, so it's not unheard of. I'd imagine you'd be able to (via the process of elimination) determine what ingredient(s) may be causing the problem (I also can't vape vanillas, they make me hoarse.)
Some stuff is more of a "sensitivity" than an allergy, but since you are under the care of an allergist, I'd suggest discussing the problem with your allergist. As, if you are going to do more experimenting, it's good to have a rescue plan in place, and your allergist may even be able to offer you the option of testing some of your liquids just like regular other allergens (although, if it's more of a sensitivity, I guess that might not be the best route of approach.
I had trouble with large, cloudy setups period, when I got here. My respiratory system was having fits, due to the damage I had done via smoking. I personally did better with small, MTL vapes (and preferred them) so the idea of trying a tank like the Nautilus 2, which can go right on your Vapresso mod, with little cost, might be an idea.
However, everything I've stated kind of hinges on the idea that you see your doctor first. As I'm sure you know, allergies can increase over time and be deadly. It's not popcorn lung though, I very much doubt. I don't think there has been a SINGLE vaper who has been diagnosed with "popcorn lung" and if you are a newish vapor, well, it also doesn't develop over night, but really, vaping doesn't cause popcorn lung, it genuinely doesn't. I'd suggest a visit to your allergist and (if he's willing to provide a rescue plan for you and some thoughts on elimination of variables) just do some experimenting with PG/VG ratios and flavors.
The ideal way to experiment is going to probably require some DIY materials at some point, so I might take a look at that forum, to see where and how you could get the ingredients you need etc.
Best of luck,
Anna