Unfortunately I have not found a remedy for my exercise intolerance. I seem to be in a similar place as you. Just go for a walk can give me a headache as well, it really ****ing sucks. I believe that some of my issues are coming from my neck, but I have been to two different physical therapist and they don't see anything wrong with it. Really at a lost on what to do next. I have also tried Buffalo protocol, and actually had some success early on with it but after I relapsed I have been extremely sensitive to headaches. I want to get back on a exercise program (extremely light of course) that follows Buffalo Protocol, but I cant risk getting a headache for hours with my current schedule of school and work.