Periods and exclusive breastfeeding

So I’m 3 months pp (10/10 gave birth vaginal ).Got my first period 12/8.By the app I should get my second period 1/7.I know my hormones are still all over the place (and we used pull out method for now) and I know there is chances for pregnancy because of that.

But is it normal to have period one month then other nothing.

I didn’t went thru this with my first because he was formula fed.