Looking For Some Direction...my Son Is 4, Repeats Himself Over

Looking for some direction...my son is 4, repeats himself over and over and over again...focuses on one topic and won't let it go for about an hour. He's way behind as far as academics...can't write, doesn't know letters or numbers by sight. Can't tell me shapes. He is one of the most emotional individuals I have ever known. Really knows peoples senses...if they are sad, he tries to comfort them, happy he laughs with them