How to do the night feedings of newborn ?

Hi Mummies, I have a question and I am already feeling guilty about it :( Our baby boy is 36 days old. We put alarm every 3 hours at night to feed him but recently due to tiredness I guess, somehow we always miss the alarm and our boy keeps sleeping for 4 hours and sometimes more. Me and my husband both get up startled and guilty that we didn’t wake him up to feed him. Has anyone else faced this ? Is it okay to let the baby sleep through at night if he himself is not getting up ? #firsttimemom #firstbaby