This is something I'm working on constantly myself. In fact I shut down in my therapy session last Monday, it was like being sedated and not in a good way - I couldn't even feel or think.
I built walls around me too. I was bullied for over a decade every day. I was at the receiving end of my father's instability and iritability and hatred of women. I witnessed dad hurt mum, emotionally and at times physically. I went away into myself. I retreated into a fantasy world.
But I am starting to feel. It takes time. And is multi-layered, the way things are with multiple traumas and cumulative abuse. Emotional abuse and neglect over many years can be like water that slowly breaks down a stone.
Journalling can help. And reading books by abuse survivors - that can really break through feeling gradually and gently.
Your therapist can tell, I expect, like mine can, that things are delicate and needs sensitive, slow and gentle support and guidance.