I will be 69 in October, if I apply for retirement benefits now the six Months after my 68th birthday count toward my benefits or I should apply for retroactive
You should probably wait until age 70 if possible, since that's when your retirement benefit rate would reach it's highest point. If you choose to file now (i.e. June 2018), you could select any month of entitlement from December 2017 through October 2018 and you would receive the applicable delayed retirement credits (DRC) for the number of months that you opted not to receive benefits starting with the month you reached full retirement age (FRA) and ending with the month prior to the month you start drawing benefits (https://www.ssa.gov/planners/retire/delayret.html).
However, if you file between FRA and age 70 you will initially only be credited with the number of DRCs you earned through December of the year prior to your month of entitlement. Any DRCs accrued for the year in which you file aren't credited until effective with the following January. So, for example, if your month of entitlement was June 2018 you would initially be credited with any DRCs you earned through December 2017, and your benefit rate would then be recalculated to add DRCs for the months January through May 2018 effective with January 2019.
Our maximization software can do all of the DRC math for you and show you the likely long term effects of your various filing options. You should strongly consider using the software prior to deciding when to start drawing your benefits.