OP I could have written your scenario- it sounds identical to the situation you are in.
My DS is nt working , taking no meds, won't seek help.
I know the hell you are going through.
One thing I would say is get support yourself- counselling if it helps.
Apart from the support you are giving him the best thing you can do is to try to find a little joy in your own life.
It is easy to be consumed when our child is in such a dark place, but it is not your dark place, and you have to make sure you don't allow yourself to be dragged down by sadness or anxiety.
That is the real struggle.
Ultimately you are two people, and this is his path- not yours.
Although your instincts scream to help and wrap him up in love actually stepping back a little will let him find his own hands on his own oars.
Of course be there, listen, talk, cuddle, drive him to appointments discuss treatment if he wants you to engage- but let him control this.
You have to for your own peace of mind- your own sanity- your own joy.