AF question

I just had my first one off of birth control. When I was on it I knew what day I would stop and start etc.  On the pill it was 4-6 depending on stress but if I know the start I always knew the stop cuz it stopped on second white pill always! This time off the pill I only bleed for 3 days?? I have been on the pill so long is this why? How long are your guy's AF usually? Thanks for the help