AF coming early

Has anyone else noticed AF coming early after coming off BCP each cycle? AF not due until 22nd for me. But just had some cramps and spotting. I know it's possible for it to be implantation bleeding but something just tells me it's not. It's just the familiar AF cramp twinge I felt. It's possible I'm just not remembering correctly because it was so Long ago but I could have sworn my cycle was always 28 days exactly before I went on BCP.