I grew up with pediatricians for parents which means I don't get as grossed out as I should by talking about bodily functions over the dinner table. It also means I can trust the recommendations I get for good layperson medical-type books. These are two books my mother is recommending:
When the Body Says No: Understanding the Stress-Disease Connection, by Gabor Mate
In the Realm of Hungry Ghosts: Close Encounters with Addiction, also by Gabor Mate
(Thanks Mom, I'm guessing you think the stress-disease one is especially pertinent to my situation.)