i have always told t's pretty soon, but it is because it's always been a "current" thing for me. new T knows I si, but does not know specifics, as I am not yet comfortable telling her.
I have not had any t's threaten to terminate me for si, but we have had many conversations about the si, and when/if it would be a prudent choice to seek inpatient as a chance to "break the addiction cycle" in the moment. I think I have been lucky in that respect. I have spoken about my si to crisis counselors and have been hospitalized by crisis workers for it, but they were never anyone I had any relationship with...

can you maybe tell your T, and also tell him your fears around telling him? tell him that the thought of talking about it worries you because you think it may increase the urges, and that you are worried he would terminate you for it?