Have you tried benzodiazapines? I wouldn't take them for a long time - withdrawal can be worse than heroin as many long time users are currently discovering after the government recently began cracking down on prescriptions.

But if they work for you, it will give you a clue that medication could be helpful, and there are lot of options that are less addicting.

Some people will say that therapy is helpful. I'm sure it is for some people, but when you have a serious neurological problem - for me it was exactly like my 'fight-or-flight' response was permanently on for some reason. The longer it would be in that state, the more I would think about it, and it becomes a vicious cycle.

You have to break the cycle for a while until your mind / body relearns how to relax.