Laxatives/cathartics And Alternatives On Campus?

Well, my campus is huge, so I walk at least 1-3 miles every day, depending on how many classes I have and how far away from my dorm they are. I have recently cut out martial arts, though, due to a heart problem, so that might be it. And i'm scared to eat lettuce and spinach and stuff because of the e. Coli scare. Maybe i'll just eat an entire can of collard greens in one sitting? I really don't eat that many processed things to begin with, but because of hypoglycemia I eat a lot of protein and normally good carbs, like oatmeal and stuff, but since getting to school it's mostly just triscuits and raisin bran that I eat for my fiber.