My son is unable to express himself saw Orthophonist and Ear, Nose and Throat (ENT, Otolaryngology) doctor to no avail?

my son is 5 years and unable to express himself;i have seen an orthophonist for three months exercise but no positive result and i have seen an ENT specialist which he says the child has no problem but he can’t speak clearly but make sound.He is very active and plays alot;very intelligent in actions