Weird AF

Courtney
So I woke up at 6:30 this morning with horrible cramps and light AF bleeding. Day one of AF. It's now 12:30 and no pain and flow looks more like brown spotting. My AF always lasts 3 days and is usually heavy day 1-2 and light day 3. This kind of flow has never happened to me. What could it be? Has anyone else had this?