My life is being ruined by my fears and phobias - how can I deal with them?
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What you have described here is a series of events that began with panic attacks, that led to obsessions about hurting yourself, and that finally developed into full blown Agoraphobia in terms of your being house bound.
You say this began 12 years ago. What happened in your life 12 years ago that may be considered a significant precipitating event? It seems to me that you were traumatized in some way. This is where a good therapist would begin his or her investigation.
Medications are quite valuable in dampening symptoms of anxiety. But the core issue that triggered all of this needs to be addressed and that requires the help of a therapist or counselor who specializes in phobias.
In my experience phobias and obsessions are about avoidance, usually of some awareness or realization, something deeply hidden that you are afraid to uncover. For example, individuals who were traumatized by childhood sexual abuse often develop phobias because they blocked out the original event. Later in life, when that awareness begins pushing for attention, anxiety and phobic reactions step in to block it.
The protective aspect of the phobia keeps you distracted so you don't have time to ponder its origins. While you're distracted with what you have projected outside of you, the secret remains buried. You do need to get to the bottom of this and a therapist can help with that.
I would also recommend journaling as a method of internal excavation. You write down all your fears and keep questioning yourself about what's behind them. You do this without editing yourself. This is 'stream of consciousness' and is a valuable tool for sidestepping those protective blocks your subconscious has now turned into phobic reactions. Just write what comes to mind and keep writing until you feel done for that session. Do this for 3 weeks and see what happens.