That's what anxiety does - it changes symptoms frequently. Mine started with shortness of breath and light headedness. But I've also had episodes where the primary ailment has been chest pain, rapid heart beat, numbness/tingling in my head, arms hands, or legs, etc etc... She is one cruel mistress.
Breathing exercises help. The way my Dr explained it, you have to take such a deep breath that it takes mental focus to handle the incoming air. It also triggers the bodies natural relaxation response. I also have to remind myself, that no matter the symptoms, I am perfectly healthy and that it's just anxiety playing it's games on me, again.