IBS
That is my official diagnosis, after many tests, including a colonoscopy and endoscopy. My doctor has prescribed prescription strength probiotics, and has told me to keep a food journal to keep track of which foods "set me off". I feel better having an answer finally, but it does seem a bit "anti-climatic". After all, IBS is just a big word to say "my stomach hurts when I'm stressed or I eat certain foods". The good news is that it's not dangerous, and doesn't have any ill effects on my overall health.
So, there you go!