I think planning to do it again is a red flag. Also, needing to do it more is a little concerning. I SH too and I knew it was getting out of my control when I brought a razor blade to work to use on breaks and always had an "emergency kit" in my purse. Trauma work is so overwhelming, it makes sense that the urge is so strong. Have you tried talking to your T about how much this has escalated? Have you found any other coping skills that help even a little? I wish I had something better to say...stay safe!