3 year son in process of getting diagnosed with autism. He has a big speech delay and can't communicate his needs or feelings. He bangs his head either by pretending to fall and hit his head to get attention or when you want him to do something or try to stop him doing something and he doesn't want to he will throw himself backwards hitting his head. I'm really worried he will do serious damage. He banged his head at nursery when they tried to get him in his pram. Any advice or good helmets that would help? Thanks