Almost certainly normal!
It can take up to a year after giving birth to get your hormones back on a solid "schedule", even without the added breastfeeding. If you're not experiencing any other symptoms (pain, very large clots, foul smell), you can relax and see how it goes for a few more months. Mention it to your Dr next visit, but it should resolve on it's own.
As long as you're breastfeeding, it may stay irregular, though- for some women it's not a factor, but for some it really IS. Also, you don't mention your age, but perimenopausal hormone imbalance can start in your early 30's, and while it doesn't affect your fertility, it can wreak havoc on your cycle. Again, mention to your Dr.
It will get better! :-)
ps- don't forget to keep taking your Iron!