Well miracles do occur because lollipop we have something in common & a point of understanding - my daughter(16) hasn't been diagnosed with a mental illness per se but the psychiatrist believes that both she & my son (9) do have a mood disorder (so as their paternal g/mother is paranoid schizophrenic they may both be too) so I understand exactly what you mean when you say
"i have to live every day with the fact that if I 'd done things differently my son may not have come down with this devastating illness . Just that one thought has had me on the verge of suicide myself on several occassions"
i too feel this way all the time although since using the ces machine my suicidal ideation has virtually stopped & my thought processes are less weird (for want of a better word).
The thing is though that when I really seriously question what could I have done differently (hindsight is great but at the time we can only do what we think is right based on the knowledge etc we have at the time!!) I realize that there really isn't anything I could have done differently.
If I hadn't married their father (hence no input of genes from his mother) I wouldn't have had them (my children wouldn't be the same with a different father) & I wouldn't be without them for anything on earth - I love them regardless & I am sure that you love your son.
Yes we both wish they were totally healthy, just as we wish happiness & so on for them but we can not "make" it happen. So presented with them & their problems we just have to do our best to deal & to help them deal.