Only sleeps 1-2 he stretches

Especially at night. He’s 6 wks old but was premature so his adjusted age would be 2 weeks old, I guess. I clearly need to wake him up more aggressively during the day and feed him more during the day but he’s primarily breastfed and has had some latch problems it’s hard to know how to do this except with pumping more and bottle-feeding more at night? The 1-2 hrs has been this way since the beginning....was hoping his stretches would get longer but no such luck. What should I try?