Are you eating enough generally? Sounds like your not and that can definately cause that *n feeling! I have always gone to the point of hunger where I couldn't eat and that doesn't do any good at all! Try to keep some snacks with you to keep that kind of hunger away!
Not eating will cause all kinds of digestive issue for you!
When you feel a panic rising try breathing in through your nose to the count of 7 and breathing back out slowly through your mouth for a count of 11, my hypnotherapist taught me this and I do it numerous times a day now, I've now found when a panic starts I automatically start to breath properly and it starts to lessen to the point where I've avoided panic attacks for the last 2 weeks!
Good luck and take good care of yourself! Hope you feel bette soon x