Baby straining to poop

FTM mom here, my son is 9 weeks +3 days and he really is a generally happy baby, except when he has to poop. It just seems like he strains so hard and he usually cries. We brought it up to his pediatrician at his appointment last week and she didn’t seem to think anything of it... she said as long as he doesn’t seem like he’s in pain while he’s eating or immediately after, then there’s probably not an issue. I’m not entirely convinced though, but not sure what else we can do for him. I nurse him as much as possible, but we do supplement as well.

Any advice would be appreciated!