Hi Harleen: It sounds like you are having a really hard time! There are a few things that I would recommend. First, don't worry about breathing correctly. I suspect you are becoming anxious over being anxious. Breathing correctly isn't the end of the world, but you can learn to do it properly.
Relax about the breathing thing. You don't need to beat yourself up. When you are able to back off on yourself a little, find a relaxation CD and use it often. You could use the one that my colleague Dr. Fee and I have produced, called Stress Less! that has some very nice sections designed to help people who are suffering just like you.
Second, find a therapist that can help you work through some of these issues. It's hard to do it alone. You can find one in your area at Psychology Today.
Finally, you might ask your doctor to prescribe something to help you calm your nerves. A short (and I emphasize short) course of something like Xanax can help you get past this bump in the road.
I hope this helps,
Dr. Diana Walcutt
The Stress Masters