3 Month Average, excluding current month

Hi,

I'm trying to create a measure which will give me an average of the previous 3 months, but exclude the current month. For example, for May 2021 I want that to be an average of February 2021, March 2021 and April 2021. 

Currently using the measure below I have been able to display the 3 month average but for May 2021 it's the Average of March, April and May

3 Month Rolling Average Fall Through = 
IF (
ISBLANK ( [Withdrawals]),
BLANK (),
CALCULATE (
AVERAGEX ( VALUES ( 'Date'[Month/Year] ),[Withdrawal %]),
DATESINPERIOD ( 'Date'[Full Date], LASTDATE ( 'Date'[Full Date] ), -3, MONTH )
)
)

This is what the average is on a month to month basis

This is what it looks like on a 3 Month Average basis

Looking at the first Visual, the average for March, April and May is 38%, 47% and 24% which gives us an Average over them 3 months of 36%. 

The figure that I want is the average for February, March and April which is 50%, 38% and 47% which gives us an average of 45%. 45% is what should be showing in the May 2021 3 month average

Does anyone know how I can do this?

I'll attach the PBIX file below

https://www.dropbox.com/s/xkoqrr1n7zabshn/Withdrawal%20Help.pbix?dl=0

Cheers,

Mike