2 weeks early

I started my period at age 13 (22 now) and have allllllways had a pretty predictable cycle. I had my last period 2 week’s ago but have been having cramps the last few days. Just to be sure (because it felt so much like menstrual cramps) I’ve been using a pad the last 2 days. Today it looked like I started and I’m really confused. It was also much lighter than normal but definitely similar to a period. Also, I’ve been on the pill for about 3 months. Anyone have any idea? I’m at a loss.