Have you been drinking a lot of caffeine lately? Sometimes things like coffee or tea can cause you to have anxiety, especially make your heart beat fast. I'm an anxious person, myself, and sometimes I get anxiety spells like yours when I drink coffee. I'll breathe slightly faster, my chest will start to kind of hurt, i'll get shaky, and i'll get panicky. So, you're not alone. Just take deep breaths and continue to tell yourself that whatever your feeling/fearing is nothing but anxiety messing with you. That you'll be fine and you'll get through it. Hope you feel better.