Oh Sweetie, every single one of us with anxiety or panic has experienced what you are going through. It's called "Health Anxiety" and is very common. Anxiety can actually create all manner of very real symptoms and once we cross over into the realm of "hypervigilism," our canoes have sprung a leak.
Every tweak or twinge, every ache and pain becomes a tumor, cancer, a stroke, MS, a heart attack...................in other words, every disease in the book.
You have been totally checked out and all your tests are negative. You are, PHYSICALLY, a healthy young man. Psychologically, you are a healthy young man with health anxiety.
Your next stop needs to be with a good therapist so you can get off this merry-go-round before it takes over your life, which, if left untreated, it will. How do I know? Because I rode that damn ride for half my adult life worried every minute of every day that I had a deadly disease. What a waste. Those are YEARS I will NEVER get back. I missed out on so much. Don't do that to yourself. You have this anxiety for a reason and a good therapist will help you figure out why and then help you get rid of it.
And for the love of Mike, do NOT Google your symptoms! Those places can turn a stubbed toe into cancer in the blink of an eye!
(I know because I had toe cancer for 3 weeks once!)
Find a therapist.
Live!
Peace
Greenlydia