Pregnant while breastfeeding

Ok this might sound so stupid BUT I know it’s an old wives tale that you can’t pregnant while breastfeeding but is the reason people thought this because you are less fertile, or is it because you don’t get a period for a while while breastfeeding?

My son just turned 8 months and I just had my first postpartum period. I breastfeed him approx 6 times per day and my husband and I want to start trying for baby #2.

Basically I want to know, now I have my period back am I just as likely to get pregnant while breastfeeding?