Anyone with musculoskeletal pain of almost any kind can probably benefit from this site: do-it-yourself-joint-pain-relief.com I can't recommend it highly enough...
Something like I am not sure what, but I do believe that hitting 40 will not do that to you, it's too early for that. Anyway please do obtain something like visit to your doctor anyway. Good niche chair is fine, I can even recommend something like gaming one.