Help! Violent meltdowns getting worse!

My 13 year old son's violent meltdowns are getting worse

 I am still sore a  week after the last one. He hasn't laid a hand on me but throws everything and anything at me,  boots, scissors, mugs anything that's in reach. He also self harms during the meltdown.

I do what they say and dont shout and try to calm him. He refuses to talk about it a day or so later once everything is calm but he wont discuss it and shuts down. He wont even try to take himself out the situation or go to his room to calm down.

He is now not engaging with the child psychologist, wont talk to anyone about his feelings.

I'm at a loss and feeling really low as I cant find a way to help him.

Anyone else going through this or have any advice how to get him to find away to not lash out?? Any online support groups for struggling parents? 

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