The Church keeps tithing settlement records back a long ways. You may be able to request a list of your tithing and total contribution amounts for years prior to those available online.
The form was called Contribution Information Request last time I used it. It asks for the year, the ward, and the stake. I am not sure if the form I have is still current (3/98), where to find a current form, or if the Finance Department is even providing this service any longer. Your ward clerk may be able to help you track it down through the Global Services Department.