Hi Junaid - this one is pretty easy if you utilize the TODAY function. I'm assuming you only have data for completed months. In that instance, you wouldn't need to include this month, and you'd just need a calculated field. The logic would look something like below:
MONTH([Generated Date]) < MONTH(TODAY())
Just take this field and place it on your filters shelf, keeping TRUE values. The beauty is that this should dynamically work for every new month without you having to change any logic, as well as being a boolean calculation so it should be fairly performant.