Help! Baby diarrhea, causes?

My baby has had diarrhea once a day for the past 3 days but he’s also had one normal poop in that time. He’s 5 months old and no fever. Not sure if I should call his doctor on Monday or is this normal & should pass? He’s never had this before but it was so watery it just absorbed right into the diaper. He doesn’t seem extra fussy and no changes to diet or anything. Does anyone have any insight?

Google is a scary place so I came here instead lol I’m a FTM and a worrier. Thanks!