Breastfeeding only once a day without pumping

Hi all, i’ve been breastfeeding once a day for 4 months but i still haven’t gotten my period. I’m 9 months post partum and i find it odd. Women who breastfeed around the clock are the ones usually go long without period. I don’t even pump through out the day. My supply is still fine.

Reason being breastfeeding only once is because my baby’s in childcare so she’ll only breastfeed at night before going to sleep. The rest of the day she’s on formula. Should i let it be or go seek medical help?