The worst pain I've ever felt was one day a couple of years ago when I was sick at home with a fever. Nothing serious, I just had a fever, headache, and a general feeling of malaise. I was at home alone in the afternoon when I got out of bed to go use the bathroom, or coming back, or something, when a hideous burning sensation enveloped my torso. It was as if my ribcage had been replaced with hot iron and was searing my muscles. I tried to take some deep breaths and walk it off, I stretched, I gritted my teeth, but it kept getting worse. Finally, I went back to my bedroom, and just as I reached the edge of my bed I think I blacked out for a second or two, and when I fell over on to my bed I came to and the pain was gone. Such pain has never troubled me before or since that day, and I never found out what it was.