Why do I get gy/flutalent on airplanes?

OK, here's my problem: as soon as I get on a plane (economy or bus. cl), I get gy. Like clockwork. I also suddenly have a huge urge to poop. Unfortunately, no matter how many times I go to the bathroom, nothing comes out except for toots. When I get back on the ground I first need to go to the bathroom, and then it spews out of me. What is going on?