I agree, it's scary, especially if the therapist doesn't bring up the topic, but they may surprise you with their response. You did so well abstaining for a whole year and falling off the wagon is understandable. Your therapist may help you identify the trigger(s) and support you if you want to stop again. They may see telling them and taking responsibility as a better sign of 'stability' than keeping it a secret. ( I hope this doesn't sound preachy, I really admire how well you have done so far and so understand the desire to start again) the best of luck as you work out what is best for you in your situation.