Help! Should I wake my 4wk old for feeds or let him wake on his own

Okay so my baby boy is basically 4wks old he was a premie at 36wks. I usually wake him at night every 2.5hrs and he eats almost 3 oz. Last night I let him wake himself and he woke himself every 4hrs and ate almost 4oz every time.

Usually when I wake him every 2.5hrs he sleeps all day except for feeds and is awake in the am ( it is literally impossible to keep him awake during the day for longer than his regular feedings sometimes he'll stay awake for 40 min. ) he sleeps so much i call him sleeping beauty

Today he has been awake for most of the morning since he actually slept last night and had a full belly on 4oz he took a small nap but besides that has been awake.

What should I do I want whats best for him even if that means no sleep for me