Spotting 2 weeks before period.

I've spotted the past few days and it's strange because this never happens. My birth control is on time and my periods still not for two more weeks or longer. I filled in my health log that I spotted for the past few days but it said it was sometimes normal during ovulation, and it was my fertile week. But being since I take birth control, I didn't think ovulation or fertile windows mattered because of being on the pill? Anyone know anything or reason why? Or have this happen?