36 weaker Milestones

B93

My son was born at 36 weeks so about 4 weeks early. When looking for milestones do I use his corrected age? I am asking because even though he is 5 weeks old all he does is sleep with very little awake and alert times. This seems normal if I use his corrected age of 1 week. I have a coworker whose daughter was born a week after my son and she seems to be doing a lot more than my son and I am just a little worried about his development.