I absolutely do relate to what you said here:

". . . experience "triggers" that set off a long series of events, feelings, emotions and actions?
One thing (no matter how small) leads to another leads to another until you have a huge avalanche of misery and physical debilitation?

This is EXACTLY what happens to me too. It all starts with one trigger and then it goes downhill from there until I have one of my emotional "episodes." One of the most difficult things about it is that somewhere in the back of my mind, I realize that I am probably over-reacting, but I can't stop. I get so overwhelmed that it feels like a crisis, and then afterwards I am so exhausted just from the stress of the whole experience. My therapist and pdoc have diagnosed with with Complex PTSD.