Thanks for the replies! He seems to be doing well socially. There is a bully in the mix, but he seems to be dealing with that ok. I immediately made the connection of a stomachache after getting in trouble from protecting his best friend from an aggressive boy. He just told me recently that he found a "true" friend, but he's pretty sociable and well-liked. I've volunteered at school just to get to know the kids in his class. He leads games at recess, so that's a good sign.
The doctor checked him quite thoroughly with blood tests and x-rays. He's healthy. The afternoon fatigue is unusual, but it could be growing pains. He seems to be popping up with new complaints every day. I try hard not to overreact and he's complained for a month before I finally, half-heartedly took him to the doctor. I knew it would likely be nothing and I was correct.
He has begged to be homeschooled for months. I work with him after-school to provide challenge. We work well together, but homeschooling isn't in the cards at the moment. That is why I think he is being affected by going to school. He sounds so hopeless talking about what he does at school. There are a few bright spots, but he's having a hard time with not spending his time learning new things.
He is sensitive to how his body feels and amazingly aware. I just wonder how to accommodate this situation.