Do you do anything that has to do with relaxations methods or exercises? Yoga? Meditation? lavender oil or peppermint oil. If you mix those two together and just the smell is very good. And it usually calms you down. Aroma therapy???
Have you tried exercising?

I have had panic disorder for years with out treatment and I have benefited from these things.
Cognitive relaxation works wonders.
When you have the attack do not fight it. Just talk to it. Tell it to come on in and tell it you are going to allow it to pass through your body. Time the attack to see if it leaves faster. WElcome the attack like a guest. Tell it you open the doors to let it pass through.

I know this sounds funny but when I do it and actually talk to it out loud it does something that makes it go away faster.

I hope this helps I am so sorry you are in pain. I was there once but now I do not have that issue. It comes and goes however. I also get the "I can not breath feeling like my trachea is closing up for no apparent reason and I would freak because I thought I was suffocating.
I get that when have had too much caffine LOL

When I get it I laugh at it. I have to have a argument with my brain sometimes come to think of it.

well take care and Relax. breath through your nose