Worried about my son

I’m gonna take him to his pediatrician to talk to her about it but I just wanted to see what you guys think. So my son is going to be 12 months old in 4 days. He still doesn’t crawl. We try to encourage him all the time and give him floor time but within a few minutes it ends in him screaming helplessly until someone finally picks him up. He at most can scoot and for some reason he’s only done it on the bed. He was 5 weeks premature, but the thing that worries me is my daughter was also 5 weeks premature and she was also on the slower end of most things, but he is even way behind her as far as when he’s doing certain things. He doesn’t seem to understand any commands either, I’m not sure when they start to recognize basic commands. Actually if I open my mouth he will put his food to my mouth like to share. But verbal commands not so much. He definitely doesn’t independent play much, he will walk around and grab random things when he walks in his walker but not much with toys. Another thing he can’t do is get himself into a sitting position on his own. He can roll onto his tummy and push off with his feet but so far no getting into the sitting position yet. No pulling himself up in the crib yet either or anywhere. We’ve really tried to encourage him to crawl but it never ever works, no matter what we do or put in front of him. He will lay there for a while just looking around until he gets bored then he will scream his head off until we pick him up. I’m just worried about him :/ he feels to me more how my daughter was at 6 months old. Just looking for some insight. 🥺 (side note: I’m not sure which group this is appropriate to post in, so I’m just guessing)