From reading that, it doesn't sound much like clinical depression but a lot like ME. Especially the digestive stuff and how it makes you bed-bound.

I've known a couple of people hit really hard by ME (it takes years out of their lives and they are constantly ill and unable to live fully), and depression follows the reality of ME... not the other way around.

http://www.meresearch.org.uk/information/whatisme.html

Both of the people I know who has ME started charting their physical state and comfort/discomfort of various bodily systems over time to try and gain a deeper insight and desperately seek some handling mechanism. Even though migraines, aches and pains were the initial symptoms, their own charts showed the upset stomach, cramps, etc being the dominant constant.

Both ended up very depressed from it... and that was without any external pressures being introduced.