Postpartum periods

Ladies, how long did it take for your periods to become regular? With my first I didn’t get my period back until 8 or 9 months postpartum and it came for two months and it was exactly 30 days apart, with this babe I got it back at 8 weeks postpartum, currently 13 weeks and 4 days postpartum and I’m starting my period for the third time in 5 weeks. First time it was 4 days, second was almost 3 weeks later and lasted 6 days and I literally ended my period on June 21st and it started again tonight. Should I be concerned and reach out to my doctor or is this pretty common?