Exclusively Pumping: Milk Supply Constant

Hi All, I've been pumping for 3 weeks now, with the milk supply averaging 90-120ml per 30mins pump session currently. I pump every 3 hours now. However, I am keen to increase milk supply per pump. Is it encouraged to decrease the frequency of pump session as I am not getting sufficient rest (confinement nanny told me to stretch it to 4 hours). My baby is 3 weeks, 5kg and already drinking 110ml breast milk per feed during the day. He drinks formula at night as it makes him fuller and sleep longer (as recommended by confinement nanny). Please help 🥺