I lost 65 lbs cuz of diet change. my upper back started hurting months ago.better with rest. starts burning when i get to work end of day its terrible?

Many possibilities: Because this pain has been going on for many months it really should be checked out by a doctor. While it could be a typical back pain i don't like the length of time or the associated symptoms (namely the weight loss - which may or may not have been completely intentional) please seek medical attention to be sure nothing serious is going on.