Rolling Six Months Data by Current Month

Dear Legends,

I am trying to create a group on rolling 6 months data to show up sales for whole year by months.I manage to write last six months but it doesnt roll up any further.

IF {@TRANDATE} IN DATEADD("m",-6,CURRENTDATE) - DAY(DATEADD("M",-6,CURRENTDATE))+1 TO

DATEADD("M",-0,CURRENTDATE) - DAY(DATEADD("M",-0,CURRENTDATE))

THEN TOTEXT(DATEADD("M", 0, CURRENTDATE), "MMM-yyyy")

ELSE IF {@TRANDATE} IN DATEADD("M",-7,CURRENTDATE) - DAY(DATEADD("M",-7,CURRENTDATE))+1 TO 

DATEADD("M",-1,CURRENTDATE) - DAY(DATEADD("M",-1,CURRENTDATE))

THEN TOTEXT(DATEADD("M", -1, CURRENTDATE), "MMM-yyyy")

ELSE IF {@TRANDATE} IN DATEADD("m",-8,CURRENTDATE) - DAY(DATEADD("m",-8,CURRENTDATE))+1 TO

DATEADD("M",-2,CURRENTDATE) - DAY(DATEADD("M",-2,CURRENTDATE))

THEN TOTEXT(DATEADD("M", -2, CURRENTDATE), "MMM-yyyy")

ELSE TOTEXT("Jan-2070")

It display Nov-2014 (01-05-2014  to 31-10-2014) Which is exactly what do I want.

But it moves Oct-2014 it only shows data for month of (Apr-2014). What do I need is Apr-2014 to Sep-2014.

I shall be grateful if someone could hep me out.

Kind Regards,

Aamir