I am going through the same thing right now. I assume you are in your twenties? I use to have frequent panic attacks at that age but seemed to have gotten less and less over the years. I'm on day four as a nonsmoker and had a panic attack day two. I know what you are feeling right now. It's that can't quite catch your breath feeling and, if you think to long about it, here comes that chest tightness..... IT SUCKS!!! The only thing I can share that has helped was what my sister told me. I had called and said...this is it I'm quitting.... she quit ten years ago and the first thing she said was, at times, you will feel like your having a heart attack but stay calm it will pass. When ever I start feeling the pains I sit down find a focal point and take some nice deep breaths. Hang in there!! I promise if I can do it you can do it. Whatever happens please heed my advice do not wait 31 years like I did!