Boobs hard as rocks/ Nipples very tender

Hi moms I’m only 5 days postpartum now I had my daughter via c section. Did breastfeeding 2days until bbg did not meet required weight gain so in hospital started supplementing half n half formula/breastfeeding. I had no milk whatsoever only little colostrum but continued to latch baby the 4 days in the hospital bbg cut me up pretty good as her latch is not quite perfect yet. I feel milk coming in my boobs are super heave and hurt. Only pumping about an ounce so my question is what to do to get more supply as I want to stop supplement formula and do full on breastfeeding and also what do for pain!