Not Feeling Well Despite Having Gone to Hospital

Hi. I am a 19 year old male. Last Friday I was at the gym working out. I was pulling weights when all of a sudden I didn't feel good. I felt faint, dizzy, very nervous, so I sat down. It eventually went away. Since then, I haven't been feeling well. I have a tightness in my chest that sometimes hurts. My left arm sometimes hurts, it feels like pressure (same in my chest). I feel nauseous, very worried. So yesterday I went to the ER. I had an EKG, blood tests, and chest x-ray. I talked with the doctor. All of the tests came back fine. This was Wednesday night that I was in the hospital. Well now its friday and I feel worse. Same symptoms above, mainly nausea. I'm freaking out. Do you think it is anxiety causing this? I don't want to die.