My Son Suffers From Anxiety, Until Recently I Thought That

My son suffers from anxiety, until recently I thought that was the main problem. Now I'm thinking something else is going on. His other symptoms include:
-cannot gain weight (very thin)
-hair loss
-diarrhea/constipation
-difficulty sleeping
-difficulty concentrating
-always hot (sleeps with fan on and window open)
-headaches
-nausea/vomiting

We have a doctor's appointment booked next week. Looking for insight.

Your thoughts?