Question bout ovulation


Ok you guys so I downloaded another app and it asked me when I stopped taken the birth control pill which was July 17 I always started my period that day the app had said my period I just had August 15 to the 24 it lasted 3 days longer then usual it said that was withdrawal bleeding from being off the pill and my ovulation could come later so I’m not really sure when my ovulation is me and my boyfriend had unprotected sex Saturday sep 1 could there still be a chance we conceived iv also read you can get pregnant soon after stopping the pill I’m a little confused with everything and need answers