Suggest Treatment For Heart Palpitation With Shoulder Pain

hi, i went to the ER on saturday due to heart palpitations that started about 2 weeks ago.. and then about a week ago my arms would fall asleep while i was sleeping, waking me up, then on wednesday i woke up with shoulder pain near my collar bone... it still hasnt went away and now i woke up today and the pain has traveled down my arm between my arm pit and elbow on the bottom side of my arm. When i was at the ER they did 2 ecg's, which were normal, blood test, and a chest xray. The doctor had thought it was a blood clot in my lung possibly, but after the blood test came back he said it wasnt. Pretty much i didnt get any answers and im worried. As far as the heart palpitations go, he didnt know what was causing them so he just told me to stop drinking caffeine. Could you please give me any insight as to what you might think it could be. I also quit smoking on wednesday when i woke up with the sholder pain. And im extremely stressed, because when i was at the ER the doctor told me i "could die" (when told i might have a blood clot in the lung) ..i have anxiety as it is.. and hearing that completely stressed me out.. my hear rate was 122 at the hospital because i was so scared, and since then, i havent been able to sleep well, i keep waking up in the middle of the night. I am a 22 year old female.