Ay girl, totally get your pag-panic kasi ligated ka na talaga, but honestly ligated (cut) is super reliable, way more than 99% effective, so buntis is extremely unlikely talaga! Six days late can happen pa rin especially if stress, lack of sleep, or kahit diet changes, lalo na you're exclusively breastfeeding pa, so hormones mo ay still adjusting pa siguro despite the ligation. That said, kung umabot na sa 2 weeks na missed period o may other signs like nausea, best to check with your OB lang para peace of mind mo, mabilis lang yung pregnancy test anyway, and once you see it's negative, makakatulog ka na ng maayos!