Show last 3 months data using Calculated Dimension in Qlik Sense

[datashaw]

Dear Experts,

I have a basic requirement to show last 3 months of the data (ie., May, June, July -2019)
So I've used the caluculated dimention in my Straight table which is

=If((MonthName(PDATE)) >= AddMonths(Max(TOTAL (MonthName(PDATE))), -3), (MonthName(PDATE)))

the resulting table gives me total 4 months including current month August Data as well. All I'm interested to see only last 3 months excluding current month

can you please correct/amend me the above calculated dimension

In my data model i have only a Date field (PDATE),do not have Month field in Master Calendar

appreciate your help on this