I have a 5 week old struggling to pass stool over the last few hours. he seems to be gassy and constipated.

How fed ????: A breast fed infant may stool a bit every feeding or an overflow diaper once a week. If it is soft it is not constipation. If formula fed, the pattern is more likely to be a few daily or at least every other day. If stools are soft & baby feeds well & plays, there is no reason to be concerned. Babies make noise & push stool with their breathing muscle since their belly muscles are weak.