I got that a little at first when I started, but admittedly I was hitting it pretty hard, trying to replicate the burn of an analog. I still vape 24mg all day erryday. I really only get nic headaches when I am trying a bunch of new flavors, so i'm doing hard puffing in rapid succession.
But yeah, might be the nic, might be the flavors, might be the PG. Do a little bit of process of elimination.