Period 5 months PP

B

Hey Everyone im 5 months postpartum and im exclusively pumping. My baby girl with nurse sometimes at night. I pump ever 3 hours from 6am to 9pm. My period came back last month but this month it is a week late. I.did have a tubal ligation when I had my c-section. Is this normal for it to be unregular? With my son i had a csection as well but period came back at 4 months postpartum and was normal after.