Confused

My periods aren't regular and I will not take birth control. My periods are always heavy and sometimes the cramps are a bit much but it's a little different this month. January 9th was my last period. This month it started February 20th and was extremely light. Pinkish brown color. I only see it when I whip and push inwards. Barely any cramping. I'm not sure what it is. I honestly don't think that I'm pregnant but I've never had this happen before.