Are you starting with a new T or group or just starting this part of your process? If you are with a T you have been with a while I would expect they would help you learn some grounding techniques and that they would have a strong enough relationship with you to help soothe some of those fears. If it is going to be a new T make sure it is a good fit and they are able to help you regulate in session and teach you how to do it for yourself outside of sessions before you start talking about things.