I started spotting 3 days after ovulation. this has never happened to me before. what is the likely cause?

Ovulation spotting: At 28, if is sometimes possible for two eggs to ovulate, and the drop in estrogen just before ovulation is enough to cause the lining of the womb to bleed slightly, just as it does when your period occurs, only much lighter. In your 30's and 40's this may happen more regularly, but it is not harmful, and your fertility options are not compromised.