I'm very worried about my child's development... He waves his arms, d…

I'm very worried about my child's development... He waves his arms, doesn't talk (he says but it sounds like gibberish). He seems to respond to his name but we have such a weak connection with him... It's scary, I cry at night. The doctor says everything is fine, that he just has a speech delay and looks into my eyes. But there's nothing they can do. I worry so much for him, everyone tells me it will be okay (my son had this too and grew up normal and healthy, don't worry) but I can't help but worry. It's hard to teach him anything, he has no interest in anything