I've also gone to the ER convinced I was having a heart attack. It turned out to be a major-league out of the blue panic attack. And I've had nights when I was afraid to fall asleep because I didn't think I would wake up. So I've walked the path you are on.
Given that you are 31, it's highly unlikely that your left arm pain is heart-related. Anxiety can cause all kinds of physical symptoms, so it's probably the reason for much of what you are enduring.
I'm not a doctor, but I'm fairly familiar with meds that are prescribed for anxiety -- and Fetzima isn't one that typically used for that purpose. Also, it's *possible* that you aren't tolerating the medication well. I've tried two other SSRIs and didn't do well with either one, so I have some experience to draw on.
My suggestions...
1. Ask your doc for a Rx for Ativan or Xanax, and take it as needed. It will give you the immediate relief you need.
2. See a neurologist just to rule out anything in that department.
But it's probably just anxiety/panic.
3. Start seeing a counselor/therapist to help you uncover the reason(s) for your anxiety, and learn strategies for overcoming it. You want someone who can provide you with cognitive behavioral therapy.
Best wishes!
you must see a medical doctor before you discontinue meds to minimalize withdrawals if this happens again don't take it :)