I agree about the ice... ice massages do numb the area for at least a few minutes... use a styrofoam or paper cup... freeze water in it... pop it out and wrap it in a wash cloth or such (or with styrofoam, peal back most of cup) and rub exposed ice on area. Make sure the paper or cloth does NOT touch your skin as you rub (or your SO rubs) Work through the cold burn time until it's numb.... Keep the ice moving so as not to damage your skin.

Being flexible could also be part of your problem.. if your tendons are also so stretchable and don't hold the bones in place, if the tendons don't go back to non-flexed status, per se. Do you sleep on your back, with pillows under your knees? Do you walk evenly, no limping? Even when the SI is out, it's important not to walk favoring one side or the other, as that will cause it to go out farther or at least not allow it to release. Taking very small steps slowly is best. Do you sit with full support around you, not on the edge of seats? IDK just some ideas.... things to check. Sorry.