Confusion...

I"m massively confused... We were referred to a diagnostic pediatrician for an evaluation of our son, who is 2 and stopped speaking. He slowly started losing words until at the age of 2, he now says mom and only on occasion and does a few animal sounds. After a thorough review of his medical, physical and all other history of his short life and spending less than a hour "playing" with him.... he was diagnosed as mildly to moderately autistic. We now have 3 therapists coming each week to see him, and one therapist tells me every time she comes how she just doesn't really think he's autistic and how she hates for him to have this label.... So who do I believe? .... There has to be some reason why he suddenly stopped talking and still isn't saying a single word.. right? I'm so confused... So i guess for now we just continue with our therapy and see where it takes us...