Breastfeeding mamas, help

Dawnn

I feel my breastmilk is drying up, my baby gets frustrated and tries to gulp when I feed him now, he always breastfeeds to nap and sleep and through the night, so I breastfeed atleast 70% of the time and give him formula when hes being babysat or when were out. He likes to breastfeed for comfort so what can I do to up my supply? I can barely pump 4oz and my little guy is 25lbs so he eats more then that. Thanks