@cambford91
Liquids can un-mix if they are not completely miscible.
To me, it sounds like your vendor added VG, PG and nicotine to the gallon jug and then shipped it off to you as is without thoroughly mixing the contents.
The 10% PG and nicotine would have risen to the top of the jug and the 90% VG would have settled to the bottom. You tried it "as is" without thoroughly shaking the jug and got one heck of a nic buzz.
If I add my flavors and nicotine in a bottle first, followed by PG and then my VG I can watch the thicker VG settling into the bottom of a bottle as I add it (I use clear btls). My flavors, PG and PG based nic rise to the top.
That's 100% to be expected. VG weighs more than PG, PG based nicotine or DIY flavors.
After you add flavors to your base (PG, VG, nic) shake your bottle very well. While your mix is steeping continue to shake the bottle every couple days. After a mix has steeped always shake the bottle before vaping any of the juice.
Hope that helps and good luck!!!