Breastfeeding and Formula?

Sandra • Spanish Educator. I Love to dance. Mom of a handsome boy💙
So my baby boy is 3 weeks old and seems to want to eat very very often and sometimes doesn't sleep 2-3hrs because every hour or hour and a half he wants to eat again. My breasts don't seem to refill that fast (and are sore) and I'm scared he's not getting enough. Is formula and breastfeeding working well for you all? What formula and how young did your baby start? Maybe I'm being a worry momma but I'm also going back to work in a couple of weeks and I want to have backup :/