I'm sorry if this was asked before, but do you take meds or even believe in meds? I take anti-psychotics for my SI. (BTW, they're not just for psychosis like in my case). My SI is chronic, sounds the same as yours. Meds can reduce the duration and intensity of the thoughts. It takes trial and error to find the right one. I was on a good combo, but after so many years, it stopped working. I was only thinking about it so you might get some relief from your thoughts.