From your description it looks like fear of losing loved once and fear of being lonely.
And that fear has currently over powered his body also.
Next Steps
seek psychiatrist opinion . A low dose of medicine will be very helpful to him. He will start sleeping which will slowly balance him chemicals.
2. just for sometime. Reassure him. example. "Dad I'm going for bath, and I will lock the door in a way that it opens. Don't worry.. and incase something happens I will call you.". inshort pre inform.
3. You will have to extremely patient. You will have to be like a parent . for time being.
Health Tips
It's a phase.