Heart tests normal, but I feel I'm dying

Is it possible that all your heart tests (echo, tmt, ECG) are absolutely normal but your heart could still be failing? I suffer from severe anxiety disorder, and I've done two rounds of the clinic, and each time I'm sent away with the advice that I'm stressed out. But my anxiety is unending -- it gets horribly worse at night to a point where I can't sleep, I feel like I can't breathe when I try to sleep, my heart is always racing, my chest feels tight, and I keep feeling an impending sense of doom. Today I woke up with a slight sore throat and I've read these are all signs of heart failure. Everyone is insisting I'll be fine since my tests (done last weekend) showed no abnormality. Could they be wrong? Is my heart failing?