What Causes Anxiety Along With Constant Heart Palpitations?

Hi, I have a lotof anxiety. I quit smoking in October, then in November I developed almost constant heart palpitations, I went to the er, they did an Ekg, and a xray, twice in one week, both ok, along with blood work, my heart rate was up to 120 the first day I went. I keep getting heart palpitations though, and have constant anxiety asIam wworried about my heart. I started smoking againbecause of the stress. I just checked my heart rate, it was 103. I am 25female, weigh 128, height 5 4 is this heart rate ok, or will Ieeventually have a heart attack? Normally my heart rate is 86-100