My 12 year old son has starting talking to himself and laughing to himself

Hi

I would love some advice from parents/carers who might have experienced this with their child.  My son has had a traumatic time in the past 3 years.  He no longer lives with me (his mum) having never been apart.  Recently his school reported that he has started being much more defiant and is talking to himself, pulling at his neck and laughing to himself.  It's bizarre behaviour that the social worker reported to me. 

He has a diagnosis of autism.  They now think he might have dyspraxia but I'm not sure about this.  He does though have learning disabilities. 

Rachael