Around 6 months ago I bought a 510 kit and a 11-mg nicotine e-liquid from MyPVShop and I'm happy about everything except for the fact that when I take 4 puffs my stomach gets this weird feeling and I, very slightly feel nautious. When I smoke analogs, I smoke about 7/day and I never feel bad. I don't know why this is happening, is this more likely to be a nicotine affect or a PG affect? Today I purchased the Pen-Style (RN4072) From MyPVShop with many liquids but this time they're PG free and 0-mg nicotine. Also, what's the difference between VG and PG? I heard that VG produces more vapor and tastes better but PG has a better throat hit. Also, is the pen-style any good, is it better than the 510 because I have the 510 and it really annoys me when the atomizer gets heated and the battery doesn't last long and you have to keep refilling e-liquid while you barely taste the e-liquid because most of it gets burned. Also, is 0-mg nicotine e-liquid any different from the ones with nicotine? If yes, how?