Don’t produce enough milk for my newborn!?!

Anyone else struggling with exclusive breastfeeding ? My little man was born at 8 lbs 11 oz at 38 weeks. I’ve been breastfeeding since he was born but I noticed around 4 days of life that he wasn’t pooping and peeing as much as the hospital said he should in those first days and he would eat from both boobs and still be crying so I’ve been supplementing with formula. Ive also noticed that he tends to spit up more after he nurses from my boobs . Does that mean he doesn’t like my milk as much as formula ?