I had to help lift a heavy object up the stairs and afterwards i
got lightheadedness, felt extremely shakey and weak and had discomfort in my arm and felt like this for a short while afterwards like I was going to die...Along with heart palpitations, and felt cold too.

What could cause this? I have had numerous heart tests and now I fear
exercise because I am sure i'm going to die any second,
i'm only 16! What's happening, please help!

This can't all be anxiety or has that just caused me to be weak?

The doctor says theres nothing wrong i've had enough tests,
it doesn't seem right though!

I'm under such a large amount of stress i'm sick of this!!!