Short answer: WRONG. It’s not an effective contraceptive; use something else
Long answer: It’s quite interesting actually! In a food-scarce tribal setting (such as when humans were evolving) breastfeeding uses up much of the female’s fat resources, which essentially puts her body into a starvation state where it does not ovulate. From an evolutionary point of view this is helpful as it allows all her resources to be channelled into her existing dependent offspring. In this setting mothers often breastfed for 2-3 years until spontaneous weaning – when the baby no longer needs her as much, it’s time for a new baby (for greatest reproductive fitness, which is what evolution is all about). So breastfeeding IS a natural contraception in a “natural” setting…but we do not live in a natural setting.
We live in a world of flapjack. 🙌 We can sate our hunger and therefore our bodies are not in a starvation state (though it sometimes might feel like they are!). Therefore ovulation technically can resume at any point, and you would only know about it 2 weeks later when your period arrived.
Use something else! 👍
When Lightning Strikes Twice 