"There are stakes in the ground exactly where my property line is.
Well,
once the street is in, I can only build 20' from the property line. I
can no longer have full use of my land. "

If it makes you feel any better, you probably couldn't have built there
anyway. Almost everyplace has sideyard reqts that are somewhere around
that wide anyway.

On your overall problem, I'd gather all the info from the town
regarding the sequence of events in the approval process for the new
street. Particularly why you were not notified of the proposed
addition of a street next to your property before approval was granted.
In every case I've seen of major changes like this, property owners
within a certain radius must be notified BEFORE any such change. Then
I'd go find another lawyer and get a second opinion.