To get the last 'x' months from the current date,
Method 1:
SELECT date_trunc('month', current_date - interval '4' month) as mydate
e.g. Current date is, 2022-01-03 19:30:00
Output is, 2022-09-01 00:00:00
Method 2:
SELECT CURRENT_DATE - INTERVAL '4 months' as mydate
e.g. Current date is, 2022-01-03 19:30:00
Output is, 2022-09-03 00:00:00