I would first change from PG to VG base liquid, better for you!! As for the gas and being lethargic after
vaping, Its probably your body repairing itself. The 1st week I started vaping, I gave up regular tobacco cigarettes immediately, I got a rip roaring chest cold, a stuffed up nose, and was passing gas like crazy!! I thought it was the e cig causing it. I toughed it out and by the end of the week I was feeling fine. I have been using the e cig for a few months now and have never felt better. If your worried about it, go see your doctor and get checked out to make sure not alergic to PG.