4 week old discomfort.. constipation? Gas??

FTM!!

We have recently been experiencing difficulties with my 4 week old trying to burp and discomfort with gas?. This isn’t all the time but becoming more frequent. He is formula fed with Gentlease. He eats about 5 1/2 oz each feed (yes, ped is aware and is okay with it) we notice more at night his discomfort. He also grunts when he eats? (Not sure if that means anything)

I try my best to sit him up when feeding him and after to help digest. He’s recently been turning red in the face like he’s trying to fart/poop and doesn’t always get the relief he needs.

I’ve tried rubbing his belly and cycling his legs, he fights me with it though.

Is he just going through a phase of constipation/gas what else can I do?!

TIA 🥰