Periods after 3 weeks

I'm a first time mum of a 11 week old. I'm breastfeeding my little one, I wont say exclusive cause say twice or thrice a week I might give him formula (2 -3 feeds per week)

I had a normal delivery, had my first period at 5 weeks and since than after every 3 weeks ( had period twice in June)

They aren't as heavy or crampy or painful.

Before pregnancy my cycles were of 28 days and regular.

Should I be concerned? Or is it normal? Heard you don't get period when breastfeeding.

PS I'm not on contraception