Are you concentrating on the symptoms of your anxiety rather than the cause?
As you probably know your panic attacks, breathlessness and feeling of doom etc etc are not caused by true physical illness. They are the result of blips and glitches in your nervous system which has become over sensitive due to anxiety overload.
So although the scary symptoms seem real enough they are in fact fakes, frauds and imposters. The normal response is to react with fear to these symptoms and to try to address them. But you can't cure yourself of an illness you haven't got no matter how hard you try.
We are our own worst enemies, our misery is self inflicted. We insist on obsessing about these distressing symptoms in the hope that they will go away. But they don't because they are fuelled by the fear with which we react to our symptoms. We insist on responding to the flash of first fear (which is beyond our control) with second fear. This releases the fear hormones that fuel our nervous sensitivity. We provide the means for our own misery.
Instead of stressing and obsessing about our fake symptoms I suggest we should look to the cause. If we can put that right then eventually the days of our anxiety are numbered. No matter how long or how deeply we have suffered.
First we should address the stresses that caused our nervous illness in the first place. These may include toxic relationships, overwork, grief, money worries, loss, sexual abuse, marijuana, shame to name but a few. Respond to these causes of your distress decisively and ruthlessly. If you're not sure how then confide in a wise and trusted friend or failing that ask your friends on this forum for many there are.
However, too often the original cause of our distress is left behind and our anxiety disorder has become self-perpetuating. We experience symptoms which cause fear which causes more nervous sensitisation which causes more symptoms which cause more fear and round and round it goes.
How then do we overcome these causes of our discomfort? I suggest doing the opposite of what instinct dictates. Our instinct is to fight this demon. You've maybe been doing that for some time. But fighting back at symptoms never works: has it worked for you? Of course not or you wouldn't be here.
Fighting only generates more stress and tension, the last thing you need. So do the opposite, accept all your symptoms for the moment. Accept them as an unwelcome guest but accept them 100%. Agree to coexist with the beast for a little longer. You know symptoms are really only harmless feelings that can do you no permanent damage. So why award them so much of your time and attention.
Refuse to fight, run up the white flag, accept those feelings for the time being. Face them but do not reward them with so much of your time and attention, they are simply not deserving of it.
When you learn to respond to your symptoms with acceptance* for the time being you lose your fear of them, you no longer react to the flash of first fear with second fear. As your nerves are no longer being swamped with fear every five minutes they begin the natural healing process just as any other part of your body repairs itself if left in peace.
Then one day you awake and realise something has changed: you have regained your quiet mind, the demons have decamped.
Great will be your joy on that day of days!
*Acceptance as a road to recovery is described in full in Claire Weekes' first book 'Self help for your nerves.'