Hello @Sweet_cheeks
I'm really sorry to hear about your sadness and guilt about your son's illness. I had the same questions of myself when our 17 yo was diagnosed with Schizophrenia and OCD last year. I felt I had caused it, because I had terrible post natal depression after his younger brother was born and I wasn't coping, I was sometimes cruel, emotionally unavailable to him or unable to be rational/be the adult in the relationship.
Our son had a diagnosis of severe generalised anxiety and panic disorder at 8yo. He had some psychosis at the time, and his paediatrician thought the psychosis was in relation to extreme anxiety. Looking back, I now wonder about that. Our son said that he has had psychosis/schizophrenia all of his life. Looking back I can certainly recall his separation anxiety at a very young age, and his intolerance of changes to routines etc. I didn't realise that children could experience such severe mental ill health so young in the context of a very loving family, in which he was encouraged, supported, given all the resources he needed to thrive. I understood severe mental ill health in children who had experienced trauma, and the research I have read links psychosis to early trauma, but that wasn't the case for our son.
I asked my son's psychiatrist if my own mentall illness had created or caused our son's mental illness. He assured me that I hadn't caused our son's illness, and that there were likely to be very strong genetic factors involved. I accepted this as my oldest step daughter, who shares the same paternal genes with our son, also had psychosis/disordered eating/OCD in her teens - I didn't raise her or parent her, so I know I didn't cause her ill health.
As parents we want our children to be happy, to avoid the challenges or difficulties we had in life, but we can't protect them from difficulties, and I would say for myself, that my challenges and difficulties made me and formed me, and without them I would not be who I am. We are open as a family about the presence of mental ill health in the family. On my side, clinical depression is rife, as is schizophrenia in some of my father's younger 1/2 siblings and their offspring (so I'm not sure if the genes there come from a different paternal link to my father's), and on my husband's side, there's been OCD, psychosis, depression, anxiety. Heck, how did we ever think our children would dodge that kind of genetic heritage? Despite mental ill health in our family, on both sides, life is still very good. We have a lot of love, a lot of laughs, we enjoy life, we are curious and seek new experiences, and refuse to be defined by a label. Our 17 yo is working as an apprentice, he has a girlfriend. He says that he wouldn't change having schizophrenia and OCD because it helps him to understand others, and to have insight. I feel so proud of his perspective, and I know that as a family, not being ashamed of labels or letting ourselves be defined by them has helped our son to accept and own his own story.
So I hope you will also see @Sweet_cheeks that it is highly unlikely that anything you did, or did not do, has lead to your son experiencing psychosis at such a young age. I also hope that you and your son hold hope for recovery, for still having a good life and expereincing joy despite the challenges that life throws at you, and that you are able to assemble a supportive team of clinicians for your son and yourself. You've carried a heavy load for a long time, parenting a child with autism brings unique challenges, and sometimes leaves little energy for yourself or your other children. I hope you and your son can take some time to heal, to recover, now that your child with autism doesn't require your constant support. We do our best with what we've got, hey? It sounds like you have been doing an amazing job of parenting your children, and your love for them is evident.
All the best
Tinker