I've always felt behind a wall of sorts. I'll explain:
It can be compared to sitting in a glass prison cell. At first it was one-way mirrored glass; that is, I could see out, but others couldn't see in; they didn't acknowledge my presence or communicate with me.
Gradually, the glass became transparent. I could see out, and they, in. I could communicate with the outside world, but it was flawed; while I could, say, enjoy a (limited) conversation, it was still imperfect; I could only enjoy superficial relationships. I was still trapped behind my impenetrable walls of glass.
The walls later changed again, and became less restrictive again. Now, there were holes in the wall, the kind you see in bank tellers' booths that let people on either side of the bullet-proof glass talk to each other. It was then possible to communicate with the outside world more effectively then ever before. I had unprecedented social freedom; I reveled in conversation, and made many new friends (I'm still rather extroverted and gregarious.)
And that is the current state of my "cell": I can speak to the people outside, but I cannot leave my walls; I am still trapped inside. I'm still growing socially, though; and I long for the day when either the walls shatter on their own, or I break them, or someone else comes and breaks them.
Yes, I've definitely felt trapped behind social walls before. I know exactly what you mean.