Breastmilk supply

I feel like my milk supply is really low and isn’t feeding my baby fully, he’s still always hungry even after a 30 minute long feeding. and when i pump i can only pump an 1oz. he’s a week old and usually drinks 2 oz of formula to supplement because i’m terrified he’s gonna get dehydrated or starved. i only give him formula after a long feeding and he’s still showing hunger signs so i can still put him on the breast and keep my supply going. How do i know he’s getting enough?? any tips?