I have spent around 18 of the last nearly 21 years breastfeeding and conceived many times while breastfeeding. My cycle returns very early after giving birth, but the first few cycles at least are infertile. Either ovulation doesn't happen or AF occurs too soon after, what is termed a 'luteal phase defect' which is apparently very common in breastfeeding women.
I agree with PP, tracking your cycles may be helpful, so then you have a clear idea of whether or not O is happening and at what point in your cycle. Good luck!