Show Hide Column using dynamic Pivot query in SQL Server

I have the following generated fees data for the months like this

Now I am filtering the data based on the month and wrote the following query

DECLARE @DynamicPivotQuery AS NVARCHAR(MAX)
DECLARE @cols NVARCHAR(MAX)
SELECT @cols= ISNULL(@cols + ',','') + QUOTENAME(HeadName) FROM (SELECT DISTINCT HeadName FROM tblFeesGenerate as fg inner join tblFeesHead as fh on fg.HeadID=fh.HeadID) AS Head
DECLARE @qry NVARCHAR(4000)
IF(@cols IS NOT NULL AND @cols <> '[0]')
    SET @qry =
              N'SELECT distinct AdmissionNo,Month,Fees, ' + @cols + '
                FROM (SELECT AdmissionNo,Month,Fees,HeadName,Price
                FROM tblFeesGenerate as fg inner join tblFeesHead as fh on fg.HeadID=fh.HeadID ) p
                PIVOT (MAX(Price) FOR HeadName IN (' + @cols + ')) AS Pvt'
ELSE
BEGIN
    SET @qry = 'SELECT DISTINCT AdmissionNo,Month,Fees FROM tblFeesGenerate where Month=''05-May'''
END
EXEC sp_executesql @qry

it is not filtering the data. but when i wrote the query by applying a bit change like this it is showing nothing

DECLARE @DynamicPivotQuery AS NVARCHAR(MAX)
DECLARE @cols NVARCHAR(MAX)
SELECT @cols= ISNULL(@cols + ',','') + QUOTENAME(HeadName) FROM (SELECT DISTINCT HeadName FROM tblFeesGenerate as fg inner join tblFeesHead as fh on fg.HeadID=fh.HeadID) AS Head
DECLARE @qry NVARCHAR(4000)
IF(@cols IS NOT NULL AND @cols <> '[0]')
    SET @qry =
              N'SELECT distinct AdmissionNo,Month,Fees, ' + @cols + '
                FROM (SELECT AdmissionNo,Month,Fees,HeadName,Price
                FROM tblFeesGenerate as fg inner join tblFeesHead as fh on fg.HeadID=fh.HeadID where Month=''05-May'') p
                PIVOT (MAX(Price) FOR HeadName IN (' + @cols + ')) AS Pvt'
ELSE
BEGIN
    SET @qry = 'SELECT DISTINCT AdmissionNo,Month,Fees FROM tblFeesGenerate '
END
EXEC sp_executesql @qry

but in where clause i wrote where Month=''06-Jun'' then it is showing data.

In simply words it is only showing data in the case of '06-Jun' whereas It must show the data based on the month of '05-May' or '07-Jul'.