Heavy af for one day. Confused!!

Nikki

I started my af late at night on cd29 which was Sunday. My flow was heavy like it usually is on the first day but then after Monday I've had brown spotting and when I've wiped I've had brown spotting on the tissue. Usually I'm heavy until day 3 and then the other two days I'm light. This is so confusing? What do you think? I took a test on Saturday and it was negative.