I completely agree with theeagle. I just want to add that it works even better if you breathe thru your nose.
PTSD is not to be taken lightly, you might want to keep on seeing your therapist.
To overcome the panic attacks, you should find out your triggers, what causes them. I know that I can't deal with crowed places, loud people, bad smell and a whole lot of different stuff. I practice yoga every single day, Tai Chi in the summer mostly coz I prefer to do it outside.
It's all a question of re-wiring your brain on how you react to a certain situation. There's a lot of books to read too. If you need more information, feel free to pm me anytime.
You can do this. sophie.
Breathing exercises frequently help a great deal with panic attacks. If you sense them coming on ..... breathe in deeply to your Bhudda Belly (all the way in ) while doing a slow/moderate 10 count. Hold shortly. Then exhale slowly from the bottom of diapharagm while doing that 10 count again. Deep breathes, slowly inhale and exhale with some control while doing that 10 count. You will learn to control those feelings that lead to full attacks. Tai chi and cho gong are also very good. DVD's are available at most libraries. You can get your normality back on track as you learn coping mechanisms for dealing with the panic/anxiety...................and then those attacks will slowly vanish into the sunset.