Irregular periods with breastfeeding

Rachel

I've always had a really regular cycle and my second baby is nearly 4 months old, I had a period in November negative pregnancy test in December because AF didn't show and today had light bleeding I'm assuming another period.

Anyone else has something similar? Is it just because of the birth or maybe the breastfeeding?

My first baby I got periods at 5 months postpartum and they were normal from the start then