I think My child has a mental illness,please help!?

Hes five. His mom, who he goes to more than his dad (they are split) has babied him. shes in, very simple words, an unfit mom. shes attempted suicide, shesgot two other kids that she cant even care for. he will stand there and just pick at his skin till it bleeds and bends his fingers backwords and whatt not. he would rather stand in a corner than play with pepole. he will just be laying in bed ro sitting down and we glance over and hes picking at his hands or body and mumbling things silently. he throws fits worse than anything and stomps. he recently screamed 'damn you' at me in a fit of anger. he cant seem to stop the picking and scratching all over. he will flat out refurse to eat something and then make himself sick if we make him eat it. is it just the way hes been brought up so far or do u believe its something mental?