This is common, mainly because our hormones don't get balanced out for nearly two years after birthing. I was sooo disappointed that the whole "breastfeeding will suppress your cycle" was a myth. (This works better in societies where nutrition isn't as readily available, I've learned.) This myth, too, is often why women end up getting pregnant months having their babies, even while they are still nursing.
What you should be aware of is that your period may very well increase markedly and become incredibly heavier than previously (I have experienced this, as well as siblings and friends), and because of the irregularity, just be aware that you might develop cysts. I was nursing and still had an ovarian cyst the size of a tangerine, which we had to keep track of. (That sucked beyond belief, because the first question was "Is it cancer?") So be aware that your cycle can be a mystery and then some until you are done breastfeeding, and that your PMS/Bleeding can be more intense than before.