Adele69, this sounds so difficult for you but there is help out there its just to find it in your local area. If you are caring for him under a formal Order perhaps you can try to access your council’s Virtual School. They might be able to point you to additional resources. It might also be worthwhile to talk with the council’s Children Services who again should be able to signpost you to some help.
It sounds as if you are a Kinship/connection carer - weather acknowledged formally or not - and that designation is likely to give you access to additional support. Have a look at the website attached. Hopefully, they’ll be able to give you some advice.
All the best