Cycle confusion 🤔

K-T • 💙 2008 👼 2015 💚 2016 🤰 2018

I’m confused as to when my cycle would start.

I’ve been on the pill for the last 2 years and my first day off the pill was 13/3 so would this be counted as CD1 or the 18/3 when I began to bleed?

Many thanks