Brown blood instead of period

I started my “period” after being a week late. The only thing different is that there’s actually no blood, just very light brown blood. I can wear a pad the whole day without changing it if I wanted to. Woke up the next day after stating and had cramps but went away after going to bathroom. Typically my periods last 7-8 days and extremely heavy with clots and extremely painful cramps and headaches. I took a pregnancy test and it was negative so now I’m just really confused. What do you think it could possibly be?