I think as you stick at it and slowly overcome your fears in small stages, the anxiety will slowly be alleviated over time. When the mind's afraid and actively (or passively) avoiding something, the body automatically experiences the effects and gets geared up for fight or flight. It knows things before we're consciously aware of them, if ever we are (it's much 'smarter' than us in that way). Facing a given situation to some degree, while terrifying, can be the surest way of alleviating these anxiety symptoms. Unfortunately it seems paradoxical to the mind, hence the difficulties we face.
I think your decision to go about changing your behaviours in therapy etc. is a step in the right direction. The mind/body can easily get stuck in a rut like this, even to the extent where we're not sure what the triggers are any more. It reaches the point where the thought/behaviour (physiology) axis needs to be retrained. I was in such a state about a year ago, where almost anything would start me off. I'd be trembling and my heart would be pounding at just the thought of going out. Slowly training the thoughts and behaviours behind this was very painful, but after about a year, I experienced much improvement (in spite of occasional relapses I'll always have to deal with).