My son isn’t talking

Hi there! My son will be 2 in April. And he isn’t talking as much as he should be... I try and make him say please and more and help but he just simply won’t. He will sit there and wait until I do what he wants. Say he wants to play on his tablet to watch his YouTube. He’ll hold it out to me, and I’ll say “say help” for a good 5 minutes and he just sits there and stares. And then eventually starts crying. He was a preemie so he’s a month behind developing, but he’s almost 2 and he only says our dogs name which is “dixie” and that’s it. He won’t even say “mom”. I don’t know what to do and his next dr appointment isn’t until he turns 2.