Is it possible?

3 days before AF was to show I started spitting. It was dark brown and only when I wiped. Nothing on my underwear. I was sure it was implantation bleeding. No AF on scheduled day. However the day after I started bleeding. It was a lighter flow than usual. As I am usually a very heavy bleeder. I bled for one day and the next it was super light. Like I could have worn a tampon the whole day and been fine. Now nothing. I usually bleed heavy for 3-4 days and then spot for 2 days after.