PP period

My daughter is EBF. We introduced solid foods at 6 months and shortly following, I got my first period. Completely normal. So I was expecting my next one to be “on time.” We use natural family planning and I did pay attention to ovulation so we should be okay but, now my period is 4 days late, compared to pre-pregnancy. I took a test one day late and it was negative so I immediately just assumed it’s just my period isn’t regulated postpartum yet since I only had one. But now at 4 days late, I’m wondering. I’m fine retesting every few days but I was just wondering, has anyone had a “normal” period while breastfeeding and then skipped or delayed the next one? I know breastfeeding can do weird things.