JB is incorrect. You do not need to have regular periods (or periods at all) in order to ovulate. This is one of the reasons some woman get pregnant not too long after having a baby. They think if they haven't had a period yet, they can't get pregnant. Surprise!
I have always had very irregular periods. Always! I have two kids. My secret?
JUST HAVE SEX!!!
Try to relax and not think about getting pregnant and enjoy having sex. If you think about it too much, you will get stressed and that stress makes it harder to conceive.
It's fine that you're still breastfeeding. Breastfeeding as a form of birth control really only works when it is your child's only source of food/drink. And even then it's not 100%. That's why one of the first post-pardum questions your OB asks is "What form of birth control are you using?"
If you want to get pregnant relax and JUST HAVE SEX. If you don't conceive in the next 6 months, talk to your OB.