I was having a lot of back issues also. They seemed to go away on my right side after having the right kidney removed, but taking out the other one isn't really an option. I went for a professional fitting and was told that my quads were too tight and I needed to stretch them out to be able to get in proper position. I also had handlebars that were too wide so got those replaced and a shorter stem so I didn't have to reach so far out. Still have some back pain but I've been working on stretching out my quads and can ride in the drops for longer periods and on the hoods comfortably.