What caused my unbearable chest pain? Two theories:
Theory 1. This is the onset of Fibromyalgia
Here are a couple of entries from the About.com about the connection between costochondritis and FM. (In the video, I mistakenly said they were from the New York Times blog).
Costochondritis in Fibromyalgia
Fibromyalgia & Costochondritis: Pain in the Chest & Ribs
This third article posits that the chest pain often seen in FMS patients is not costchondritis at all because it is not caused by inflammation, but rather by Myofascial Trigger Points (MTPs).
Theory 2. Inflammation from Chronic Viral Infection in CFS
Typically, medical websites on Costochondritis say that it can be caused by two things: trauma and inflammation from chronic infection. Trauma is ruled out for me -- I haven't done jack squat in a long time! But to the extent that ME/CFS is sometimes suspected to have a chronic viral infection component due to weakened immune system, this may have caused inflammation.
Frankly, I'm not sure if these can really be considered two distinct theories, given the close connection between ME/CFS and FM. I haven't yet bothered to research much about FM since pain was never a component of my ME/CFS until last Thursday. Hopefully this is just a brief episode and I don't need to learn more about FM.