Hi Jennifer,
I also get this, I have had blood tests, ecg's etc also. My tests also always come back fine & the next time I feel the symptoms I think they may have missed something. I think it is what we focus on at the time. I have a high fever today, the flu has been going around, my husband has had it (it was not pretty!) and one of my children has had it - but to me I am so scared of dying right now. I cannot focus on anything else & I am seeing my doctor again this afternoon (second time in 4 days).
My left arm has been numb all morning - with chest pains. I was fine yesterday... but add something to the mix that can send the anxiety through the roof & now I have it in my head that there is something seriously (and imminently) wrong with me.
It has to be anxiety. :)