Withdrawal is one of the coping mechanisms I developed to survive a childhood where I witnessed violence and abuse. To protect myself I would hide away all my emotions so the bad stuff couldn't hurt me. As an adult, I hide away my emotions when facing difficult situations, I also tend to withdraw physically and become isolated, again so I can't get hurt. Do you think that this is what your therapist means?

Your therapist should try to draw you out of the withdrawn place, maybe by talking about things you enjoy or maybe by focusing on your strengths. It is a two way process, you'll have to meet your T halfway, so if you don't understand what they want you to try let them know. I made the mistake of thinking I was engaging only to be told on the last session I hadn't engaged at all. I hope your therapy journey is a good one.