The Speech Therapist... should have given you more information/resources to help. That is her job.
My son had a speech therapist... that is what they did.
It was via the Early Childhood Intervention organization, in our State.
THEN, once a child is 3... the services are done with. Since they service kids up until 3 years old. BUT... if the child needs more speech help/therapy... they are supposed to give you resources/organizations/schools... that can help and the then enroll the child into that chosen program. Per the parent's request... PRIOR to when services ends for your child.
But enunciation of words... is also age related.
My son was advanced developmentally in many areas.... except he was speech delayed. AND the Speech Therapist clearly explains to the parent... all about developmental age-related stages of enunciation and sounds of words and what word sounds are developed at what ages.....
and they work with the child... on it.
Since your son had a Speech Therapist screen him again... well didn't she/he have anything helpful to you and your son? Besides just saying his mouth is growing and his tongue is lazy?
Does not seem like a good Speech Therapist...
AND the Pediatrician is NOT a Speech Therapist, so he/she would NOT know how to help your son's speech.
Your son is young... I don't know of any kid that age, that speaks perfectly or enunciates every sound... perfectly.
It is not the blanket.
all the best,
Susan