Speech delayed

Hi,
My 3 year and 5 months year old son has speech delay he can sing his rhymes clearly ,can say A to Z Alphabets in straight and reversed ,1-100 numbers ,he is very good in numbers ( can start from any number and he continues)shapes colors and objects,but he can not communicate he is non verbal,he can not understand and follow the instructions
Never calls me or someone else
He loves to jumping on the bed and loves to be on inadequate or phone and he knows exactly which kids app he has to go to watch all cartoons. He doesn't throw any tantrums ,he listens to what you say but he doesn't get in loved with any other kids seems to enjoy his own company moving around ,playing with his toys , no potty trained yet but when we tell him to go toilet he will put his toilet seats pull his pants down and do his job ,but I think he can't express or go on his own.

Can you please help and let me know what medication can improve his behaviour and capabilities to understand and express his needs.
Note: he was preterm baby 35 weeks ,c sections .

We had also done is fragile x syndrome test , but there is nothing to worry.

And