I have this problem as well. You aren't alone.
Imo, the father of lies is attacking us in this area specifically it is the sin we (I'm guessing this is true for both of us) most fear committing.
Getting outside and taking a walk sometimes gets my mind on other things as well-not full-proof, but still helpful.
Also, I don't know about you, but I tend to hole up with my laptop and isolate myself. When these things start, I find getting out and talking to people helps me get my mind on other things. When I'm alone at these times my neurotic nature makes everything worse.
I think there is a lot of truth in Volnutt's words. You might think about very practical, non-spiritual and non-religious changes you can make to avoid the situations when the thoughts occur.
Maybe, for example, stop saying the Gloria for a time. Replace it with another prayer, if you wish. Also, the Orthodox don't always say "In the name of the Father..." when they cross themselves. They might also say, "Lord, have mercy," or the Jesus Prayer. It may not be necessary to recite any verbal prayer at all -- the Sign of the Cross is an extremely powerful prayer, absolutely necessary for spiritual warfare. We discussed it in a recent thread.
My thought is that moderation can go a long way in healing illness like this. I might examine what leads up to these attacks for you. Like Volnutt says, are there times you hole up, and do the fears follow them? Then avoid doing those things, or do them more moderately. Even certain foods, in excess or not, can trigger certain moods. Illness, physical or psychological, often doesn't just "happen" to us. We often invite it through our own immoderate living.
I am not at all suggesting that your fears are "merely" psychological. But it seems to me that the adversary can use our preexisting fears to tempt us and snare us into despair, or into crazy actions that we use to escape the pain and confusion. If nothing else, satan loves to see us suffer. One trick he has is to get us to use religious activities as a magical practice to keep away fear and confusion. (Please, will someone who is wiser me correct where I am wrong.)
Just work on doing normal things in addition to your prayers. Nothing out of the ordinary -- don't worry about special breathing, purifying diets, or marathon sessions of prayer or spiritual reading. Your attack is a symptom of your own injured nature.
You need a priest you can talk to. Just make sure that his parish is registered in his Bishop's jurisdiction! There are some not-so-legit priests running around -- I know firsthand.