is there any way to go back more than four saves?
Oh dear, maybe you are new to games?
You know, autosaves are handy because you don′t have to do anything. But the problem is that they are overwritten so often.
By pressing Start and going to the options, you can manually save the game; and those savegames are only ever overwritten when you decide to do so. You can have as many of them as you want (or as many as fit on the HDD).
Actually it is recommended that you deactivate autosaves completely in the options and ONLY save manually.