The lights are on but no one’s home

LO is turning 3 months in a few days and is so behind on social development. He only smiles when he’s about to or just finished pooping. I think he has maybe smiled genuinely at us once or twice? But at this point I can’t be certain if my memory is correct. He also does make a lot of noises but never seems to do it “in communication” with us, as in no back and forth, no social aspect of it. I can’t tell if he even knows who I am, I can’t tell if he needs me. I am exclusively pumping and not nursing too, so there’s no indication that I mean anything to him. I’ve seen that he is too young for me to worry, that maybe he is just slow. But is it bad that, whether or not I should be worried, I feel a bit heartbroken? I keep reading about how the first baby smiles just melt your heart and make everything ok. I have PPD as well so maybe I am just clinging to this way too much, waiting for the moment that will be true and it will make everything better for me.

Has anyone else felt this way?