How long has he been back in school?
We've seen a lot of exhaustion in our house in transitions into school, particularly from kindergarten to first. It's just plain tiring. We get a lot of mileage from battening down the hatches, making for a calm evening, and an early bedtime.
That being said, you seem to be identifying a lot of signs of anxiety. The feeling sick when not ill can very much be real feelings of sickness arising from anxiety.
Yes, inform the teacher of what's happening outside of school. Nightmares and feeling sick before the school are signs that he's not adjusting to school. Beyond teaching kids to read, one of the primary jobs of an early elementary teacher is to ensure that the children adjust to school. The teacher ought to take this very seriously. Then go to the councilor, or better, have the teacher work with both you and the councilor to address the situation.
While not as bad as master of none's experience, we haven't had great luck with the councilor -- it just wasn't the right fit. We have, however, had good luck by finding one special person in the school who gets my kid. It's a bit of trial and error, but we have found the right person outside the classroom eventually for each of my kids.
