Past 3 month rolling average using a measure

// First of all, you should number your months
// throughout all years starting with 1 and
// moving by one till the very last month in
// the calendar. Do not use Year Month Number
// which I believe resets every year and even
// if not, I guess it's not consecutive. You
// have to have a field that numbers all your
// months consecutively and does not reset
// when a new year starts. Let's say such a field
// is called MonthID (because this is what it
// really stands for).

// You have to put fields from the Date table
// onto the x-axis for this to work. You should
// never ever use fields from fact tables in
// any of your visuals. This is only allowed
// if you troubleshoot. Users should never be
// able to slice data via fact table's fields.
// Best Practice? All such fields should be
// hidden. Even more, the fact tables should
// always be hidden. For measures, a separate
// table should be created without any fields
// and measures should be stored on this very
// table.

// Then you'll write:

Total Awareness =
VAR MonthsInRange = 3
// Get the last visible month's ID.
VAR LastMonthRange = MAX( 'Date'[MonthID] )
// The first month for the calculation will
// be the one with MonthID removed (MonthslnRange - 1)
// times since you need MonthsInRange months in the range.
VAR FirstMonthRange = LastMonthRange - (MonthsInRange - 1)
VAR ThePeriod = // don't hard-code numbers in the names
    FILTER(
        ALL( 'Date'[MonthID] ),
        FirstMonthRange <= 'Date'[MonthID]
        && 
        'Date'[MonthID] <= LastMonthRange
    )
VAR Result =
    IF(
        // This effectively makes sure that
        // you've got 3 full months available.
        COUNTROWS( ThePeriod ) = MonthsInRange,
        CALCULATE(
            AVERAGEX(
                ThePeriod,
                // Make sure this measure is correct!
                [% Aware]
            ),
            REMOVEFILTERS( 'Date' )
        )
    )
RETURN
    Result