I think in your case the SI is the one who's giving issues. In my case the SI doesn't intervene at all. First of, I'd suggest making sure you're 101% sure of going through with it. Second, you could try something like benzos, to calm yourself down and reduce anxiety. Maybe try finding a position that doesn't hurt the rest of your body too much; some positions I do are kneeling down on both knees, sitting with legs crossed, or even crouching. Basically a position that doesn't hurt your body but, at the same time, allows for partial to take place. Hope it helped