Please help me I'm desperate

I posted a few hours ago for advice on respite care for my Autistic son, I'm sitting here holding bad the tears so my husband doesn't know, can't talk to him as here's had years of stress and is on chemotherapy. He's not son my biological father but as been a good dad to him but he can not take anymore stress and as had to walk away. I'm desperate and feeling alone in this, I'm afraid for my welfare and mental health, I'm dreading everytime the phone rings in case it's my son threatening to kill himself or harm I've got no energy left in me to fight anymore. I wish I could magic money so I could afford the places that he could go to but I just don't have it.

Please does anyone know of any services that assess for immediate respite care for him. Our mental health service doesn't understand autism the last time he had them involved they were ment to send someone round to see him the next day after discharging him. Only to find they forgot which ended up in cutting himself up as he felt no one care and he was worthless. 

I live in the Warwickshire area. I'm desperate and really don't know how longer I can't cope. 

Julie