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I definitely think you should tell your therapist. Even though a little part of you is saying not to do it, you don't want to hit a low point where you feel as if you are about to act on it and have nobody to turn to. You are important, your health and safety is important, and your recovery is important. You shouldn't have to deal with all of these thoughts all by yourself and it can be really beneficial to you to have your therapist by your side to get you through all of this. If she brings up sending you somewhere you can ask her if there is anything else she can try first, but remember that you deserve to be safe and to get through these thoughts.