View attachment 114357
You may, as stated have an "allergy" (read: sensitivity) to Proplyene Glycol. If you place a drop of pure (USP) PG on your skin, it will turn red and become irritated very quickly if this is the case.
It may also be that you have juice that's made with non-USP PG or VG, both of which can irritate your lungs, and give that "I smoked 3 packs of cigs last night" feeling. Keep in mind that even if your base has USP pg/vg, the carrier for the nicotene may not be USP (Common with chinese juices like Dekang)
You also could have inhaled a small amount of liquid, which, if you are using even a USP PG juice, cause your lungs to "seize up" a little, causing an irritated feeling.
Other causes could be using a juice that has a "buttery" flavour, as it contains Diacetyl, which is not meant to be vaped and can cause chronic bronchiorespiratory issues.
It could be environmental as well, of course. It is the peak of summer, and it's hot, humid, and there are a buttload of allergens floating around, particularly if you live in a densely populated area.
I find that if I vape on a high-condensation tank or atty, I get the chest tightness... this is to be expected of course, switching kit sometimes helps this to a degree...as does putting down the vape and doing some deep breathing excercises for a half hour or so.
There's never any harm in getting a checkup, particularly if your Dr. has been on you to quit smoking, it's fun to educate the professionals
It is also possible that you have inhaled bugs, birds, small mammals, lung goblins, or microscopic extraterrestrials from a parallel universe.