Well done first of all. I stopped smoking about 8 years ago so i know how difficult it can be.Your symptoms seem a little extreme for just nicotine withdrawal and are probably more related to your general anxieties/panic symptoms which are being activated by your perception that your losing a crutch you've had.
When you feel really bad just try to remember to breathe (focus simply on your breath going in and out and how that feels - it may sound trivial to some but when you focus your attention absolutely on just the flow of your breath and the related movements (chest and abdomen) of breathing it stops you thinking about other things/stills your mind) - can be really helpful at difficult times and reminding yourself that these feelings will pass also helps. In the early days the intensity of you withdrawal symptoms should peak and dip across the course of the day rather than being constant - try to keep occupied.
With regard to smoking and withdrawal the first 3 weeks or so are the most difficult.To be honest all that happens with time is that you go longer and longer without thinking about smoking/feeling like a smoke rather than ever suddenly being over it but it is easier to do as you can build on your growing success the longer your off them. Allen Carr's 'Easy Way To Stop Smoking' is a great book my father quit and has stayed off cigarettes for over a decade after smoking 50-60 a day for 40 years after reading this book - i used the same book which also worked for me. Whether you lapse or not i suggest you get yourself a copy.
If things don't improve over the next couple of weeks you should maybe consider addressing your underlying anxiety issues.Hope things improve for you soon - Best of luck, don't give up - you've already taken the most important step -it will improve :-)