It's possible to get your period while breastfeeding. A lot of people don't think it is, but it is. However, it may not be until you're done breastfeeding.
I got mine right after I stopped breastfeeding 8 weeks pp.
My sister in law didn't have hers for 9 months because she was breastfeeding but got it while breastfeeding when she was 2 months pp with her first baby.
I guess when mother nature feels like it.