Welcome to the family
And to answer your question, no you're not crazy. You are having panik attacks. You did all the tests, went to the ER, and all is good. This is your anxiety acting up. I know it because it happens to me all the time (exactly the way you've described it). Your physical symptoms are all real and painful and scary. However you are NOT in any imminent danger. Do a little test: when you feel like this, go on your computer and watch a funny video on YouTube or call a friend and talk to them. Distract yourself for a few minutes and I bet you that you will feel much better. If you were really ill, a distraction would not cure you.
If that does not work, come back here and talk to us. There always someone here to listen, and help you feel better. I hope you feel better.
Hugs
Eli