I had not heard of the cluster headache theory (I'm very new to mushrooms) but I've now read about it on Erowid* (which I'm new to as well) and how the headaches happen in cycles, is very similar to how I experience my back pain. I definitely think more research needs to be done. I know I will be testing shrooms in the future.
*As I'm very new to Erowid, and I don't know how to navigate the site, I don't think I can put my report on there. However, I would love to get it out there and hear from others with similar experiences, so If you would like to put it one there for me, that would be super wounderful, and maybe you could put a link in these comments for me, and others who look here.