Hello and welcome! So sorry you are going through this with your son. It would be so hard to watch that, and feel helpless I'm sure!
Dianosing mental illness in children is not easy, there are so many factors to take into account, growth and development, behavioral stages, influence from his peers, etc.
It is very clear from his behavior that an evaluation is absolutely necessary! You need to ask your pediatrician for a referral to a child/adolescent psychiatrist (cannot be a general psych or adult psych, very different processes!). Allow your son to be thoroughly assessed by a specialist who can offer some suggestions. His behavior is not typical for anxiety disorders, there may be something else going on. The sooner you start this process, the sooner you can start whatever treatment may be needed. Most times, for younger children, like your son, behavioral modification is the preferred initial treatment approach. Let's hope that this if just some attention seeking behavioral stage, which can occur based on things going on in the child's life (ie, moving, divorce, bullying, etc).
Best of luck, please let us know what the specialist says!
thank you, I'm waiting for his referral to see a doctor to come through so we can find out how to help him :) xXx