Worried about my son😓😥

So...I'm a FTM and my son is about 2.5 months old. Has also been super gassy and pooped at least 3-4 times a day, just like a normal baby. But I'm worried..he hasn't pooped in 3 days, I know the next one will be an explosion, and trust me..I'm prepared for a mess. But is it normal or even okay for him to not have popped in that long? He doesn't act like he's uncomfortable, he's his happy normal self, and it could be coincidence, but he stopped pooping after I ran out of his vitamin D drops. Not sure if those can have an effect on poopy diapers, but I thought I'd throw that bit of info in. Someone please tell me that this is normal😓 I feel bad and don't know what to do to help him poop. I've been considering calling his pediatrician to get him in asap or just taking him to the emergency room, is this normal for a baby? What should I do? Thanks in advance for the helpful advice☺️ my sons butt thanks you as well lol😁