Breastfed baby, straining to poop.

I’ve read that breastfed babies tend to poop less often and can even go a week without a poop. But my son is 4weeks old and he is straining and grunting to the point where I think he’s finally passed one, but then I check his diaper and... nothing. He’s very gassy, and he used to poop after every feeding. He seems so uncomfortable and turns solid red in the face while he strains before letting out a cry, so I can tell he’s in pain.

I feel so bad, I don’t know how to help my baby. Pediatrician said probiotics, well that haven’t helped the situation at all. Wondering if anyone else has experienced this and what helped.