preemie stomach size

Emilee
My 6 week old was 5 weeks early. 
He is breastfed, but my nipple cracked so we are pumping until it feels better. 
He is only eating anywhere from 1.5-2.5oz 
Is that normal for a preemie baby?
A 1 week old baby eats around 2oz and he would be a week old if he made it full term.