You can create 2 parameters - one for month and the other for year - to use as filters (so you can choose how many months/years to go back)
,then create a calculated field (true/false) asking if it satisfies both month and year restriction.
Place that calculated field on the filter shelf, and show 'True' only.
I would've demonstrated it to you if you included the packaged workbook. But, please let me know if you had further questions.