I'm bleed at the wrong time?

I am extremely regular I get my period The day eves says I'm going to get it and it ends the day eve says it's going to end well I am four days till I start my next period And yesterday I started spotting it was so light I almost couldn't tell but I had blood on my panties and when I wiped I could see it on the toilet paper but it was very light and it was just for a couple of hours I'm not bleeding at all right now and I'm so confused on why this happened could anyone tell me? Or at least give me your opinion? It would be greatly appreciated.