Making a safe nest for him at home, free from any comparison or criticism (implied, inferred or overt) is what he needs you to do right now. Make his nest as safe as possible for him. Make sure he knows for certain that you're not going to judge him or try to persuade him out of his nest before he's ready. Make sure he knows for certain that you feel positive about his need for his nest time, not fearful and anxious. Make his nest feel as safe as you possibly can and, while he's healing, bring the sparkly to him. And make sure it's things he finds sparkly or you genuinely believe he might find sparkly if he eas aware of them and *not* stuff you think he ought to find sparkly or ought to engage in even if he doesn't.
Focus on healing any part of your relationship that has been damaged by schooling as well. Look up Maslow's hierarchy of needs and remind yourself that your job as an unschooling parent is to make sure the lower levels of need are met to enable the higher ones to be possible - safety and security, food, sleep, relationships. And seek to create joy from what he's able to do right now.
Focus your energies on those priorities and watch him and you will begin to see signs of healing; you'll begin to learn who he really is without the influence of schooling and all that entails.
If you do this healing time badly—forcing him to do things before he is ready to or when he has no interest, judging and fearing his need for a healing nest (you wouldn't fear a plaster cast and time not playing football and etc. if he'd broken a leg), the healing won't happen and you're unlikely to see the return of joy and self-confidence you're hoping unschooling will lead to. If you do this healing time well, you will see him flourish; you will see your relationship strengthen and you will begin to really know your son and what makes him tick and you will get better and better at responding to who he really is.