Are you really sure he's physically fine? Not constipated, for example? What changed this week?
I was thinking along the same lines. Even though it may be related to anxiety...he really could be experiencing a stomach ache. I was notorious for anxiety-related 'tummy aches' as a child. Looking back, they really did hurt - I just didn't associate them with a feeling at the time.
Maybe you could try the "back door approach" with asking some questions about school...
Let's see:
DON'T attempt to have an information gathering conversation when he first gets home from school or is playing a video game/watching tv/etc.
Try to catch him when he is opening up naturally, maybe while having a snack or in the car? Maybe you could share a story of how you experienced school as a child and get him engaged in asking YOU some questions. You might see him project a lot of his feelings onto your story. Or you might find that he will less guardedly begin to discuss if there is an issue at school
There is always SOME issue at school to some extent. Sheesh, these little guys are trapped in a class with twenty-some odd other bouncing pinballs for 6 hours! Social hierachies develop quickly. School lunches stink. PE teachers are mean...
If he still complains about the stomach, you may see if his doc can at least rule out fixable/identifiable physical issues anyway.
Poor kiddo...it sounds like he's not happy with school.
