To find the report you used before
Navigate to Reports > Builder
In the left menu click Recently Used Templates, you might find your report here.
To make sure you can run the same report every time
Click the STAR on the Template screen which will save it to the Favourites Section
To retain all the configuration and settings, once your report is constructed as you require, SAVE
Add it to an existing Bundle or create a new one
To make you bundle easy to run every month, review the date settings so you only have to check the Report Month in the orange banner each time you run the bundle.