My period started a week early. Why???

Zoë

I've been on the pill for a year now and my periods got easier but they were always about on time (no more than 2 days early/late). I always take my pill at the same time every day. I'm still on an active row. I've been medium-stressed lately but I've definitely been way more stressed in the past and this didn't happen. What is this BS??? Anyone else experienced this???