Like the above, I am not a psyc, but I am also the CL here -
http://www.medhelp.org/forums/ADD---ADHD/show/175 - and have seen what can happen to a child when you know something is wrong and no one shows you how to cope.
My guess is that as a child your response was how you dealt with either anger or frustration. What was causing that - I don't know. Many times being very smart and not being able to communicate the way you want to is highly frustrating.
Anyway, then things got worse and you tried to compensate the only way you knew how.
I think you finally found out that to move forward, you had to wall yourself off from that which was hurting you. Which is sad, because that is the opposite of how to deal with the situation. So for years you have used this filter. And it is now pretty much a part of you in that it is like a habit gained through constant practice.
It can be unlearned. But, you will need help on this journey. It sounds like you have not had any one you can trust for years - which makes it even more difficult.
You do show slight symptoms of being on the autism spectrum, but that could also have been due to your environment growing up. But, it probably wouldn't hurt to research it. And possibly something like ADD which might explain your frustration and anger between 4 and 10.
But, I do agree with the above writer. Even though you are highly intelligent, I don't think you want to take this journey alone - at least not at the start of it.
Oh, to answer your question, (in my opinion) your behavior now is because what you did as a child did not work for you. If you had someone you could have talked to...like a school teacher. If you were into exercise, or yoga. If you had found any other way to deal with the situation,besides walling your self off from what was happening to you, things might be different now.
However, the fact, you are now looking for answers is a good thing. If, I/we can be off any more help - please ask! Best wishes!!!!!