Confused, Help?

So I just had my period 2 weeks early and it was definitely nothing like my normal period. I have a 36 day cycle with a period lasting 8-10 days. But right after my fertile period ended I got my period (2 wks early). I had no idea it was coming. I had no warning. Before my regular period I ALWAYS have sore breasts a the entire week before my period. And 3-4 days before I get it, I also get cramps. I am very regular and have been since my first period at 14 y/o. This strange period only lasted 4 days and the flow was very inconsistent and constantly changing but never got as heavy as it normally does.

Does anyone have any idea or advice?