My fertile window changed!!!

Teneale • Never ttc again but we're ready for baby #2 😊
According to glow my fertile window was supposed to be from 13th - 19th March took my bbt this morning and Noticed this morning that it changed. Is now saying last day of fertile period was 17th and that it started on 11th and now I'm freaking out because we missed the first couple of days!! Does anyone know why it would have changed mid fertile window?? I'm super sad because we didn't bd until morning if 14th!!😔