return of menstruating
I was almost exactly like you, except a little more delayed. Natural birth, exclusive breastfeeding. Got my period at 14 months (which seems pretty close to norm for my family.) But when I did, wow! My cycles were so heavy it was almost scary. Totally unexpected. Of all the advice you get as a new mom, wish someone had warned me about that.
For me, it took 7 months to be back to normal. For you, hopefully it'll be faster.