Is it possible to get pregnant while breastfeeding?

I just had my son in August, and I am breastfeeding and plan to breastfeed until he is one year. But my husband and I want to start trying for a second baby and when my son is a year old.

I’m almost three months postpartum and still have no period! I feel like if I keep breastfeeding for a year I won’t have a period and we won’t be able to get pregnant with our second one as soon as we want? Anyone have experience?