Breastfeeding making AF late?

Eri
AF returned when my baby was 6 months old and has been regular ever since (it has been a year now). For 1 week during my last cycle she was sick and wanted to nurse a lot more than usual. Now AF is late by 5 days (which never happens) but I'm getting bfn. Anyone experience their regular cycles being thrown off due to a short time of increased breastfeeding?