B.L.
It is normal for your period to be irregular for a while after childbirth.
With all three of my pregnancies, I started menstruating again after about 18 months, and was somewhat irregular for another 6 months or so after that. Now, I was nursing that whole time, and I seem to be at the far end of the spectrum on this.
If I were you, I'd give it at least another 6 months or so, but if you're concerned, go ahead and call your doctor and see if they're worried at all.