issues with 2 year old.

My son is 2 years old and 3 mths (27mths), he is a active and at times quite funny.
the Dr and I are very concerned with his speech, he has about 6 words in total that he says and his only combo is "gotta go" that he says when he wants to go outside. he likes to close his eyes and walk backwards, also if he thinks something is funny he will lift his head and close his eyes as he attempts to walk to whatever it is that amused him, i feel he is a smart well manered boy at home, he took to potty training like a champ he's 100% if hes not wearing anything, and about 70% if hes got underwhere/pullup on, i think he gets confused that they arnt diapers, he dosnt mind being wet/dirty, but if something gets on his hand he freaks till we wipe it off, but he dosnt mind "dry" stuff like dirt. in public hes a completly diffrent child, hes nearly un managable, he yells nearly constantly if hes not upset he will constantly call out a repeted sylable like "GAH..GAH..GAH..ect" even tho we tell him Shh, indoor voice, tell him to knock it off, try to ingage him in conversation/narration of what were doing, or ignore him. he cowers away from other people and screams if they make eye contact or speak to him, Heven help us if hes eating when these people do that, as he will cower and hunch over his food craming it to his mouth like a starving wild child. in other social setting hes fine, we attend MOPS and hes fine, dosent cry when i leave and is the last to stop playing, he dosnt like to play with children his own age and prefers to play by himself or with much older kids 8years+
the Dr is recommending a full work up of his speach and mental abillitys and mentioned autism as he handed me a stack of yes no sometimes paperwork on him to fill out
his father is dead set theres nothing wrong with him "we just dont work with him enough" when thats all i do sometimes to the point where our 5 mth old is disadvantage
would you recommend testing for his "issues"

[Odemus]

i forgot to add,  his like a light switch,  you never know if when entering a sitiuation if the swich is fliped to On or Off