Advice and help

I have a 20yr old son who doesn’t leave the house..he won’t shower or have a shave etc, and hardly talks to me...he does however talk with friends on computer when playing online games etc...I know this is very unhealthy for him not showering etc or leaving the house . He doesn’t even go outside into the garden.
he is on the autistic spectrum but we don’t actually have a complete diagnosis as he wouldn’t talk to any specialists when we tryed to get him diagnosed some years ago...
also, he used to receive UC but that has been stopped not so long ago but he won’t tell me why , I have told him that he might be able to receive ESA and told him to ask about this on his “journal” for the jobcentre ..( but he hasn’t ).I feel so helpless and don’t know what or how I can help him..
please help??