early and late AF. any knowledge of why?

Beth • Mama to 2 beautiful girls 💕 Secondary Infertility, baby #2 IVF w/Icsi 💉 God is good 🙏🏼
Every so often I have a cycle variation of like 5 days. I'm only on cd22 and aunt flow is ALREADY showing up when for months I've been on a 29 day cycle. Any one have the same thing and find  out why?