If you're exclusively breastfeeding (feeding at least every four hours around the clock) your ovulation will probably be suppressed enough that you won't get pregnant. It's not one hundred percent but it's just as good of odds as condoms/the pill used by average people that mess up on occasion! After your lo starts sleeping through the night (experts define this as five hours or more in a stretch) or you start introducing foods, it is more likely that you'll conceive!
If you are planning to have another one quickly, take extra good care of yourself. To support pregnancy and milk supply you'll need an extra nutritious diet, daily prenatals, and definitely stay away from booze/smoking.
Good luck!
Can possibly be a type of BC but not a recommended one. But since you re trying, no worries there... Also, it is likely that if you haven't had at least one normal period yet then your body hasn't had a chance to "reset" and get ready for another baby.
Breastfeeding can prevent your period from returning for a while and can actually be said to be a birth control in a sense.