It's hard to say without knowing you, your health or any prior illnesses (Not asking you to share, just saying that history and info do play a huge role in diagnosis)
Like others said, it sounds like stress is causing some pretty bad tension and anxiety in your body. It was a paramedic who sat me down and fully explained how powerful stress can be on your body. Sometimes you don't even realize it, you can trick your mind into ignoring the signs of stress but it won't change the fact that it's still there. It can cause the nerves to tighten up, causing sharp pains, and cause your heart rate to increase, raising your blood pressure and causing the trembling you describe. The side effects are virtually endless.
My neurologist explained that anything major, such as a tumor or HIV, would have far greater side effects than those created by anxiety, and would be blatantly obvious in a blood test and in all the imaging I had done.
You did the right thing seeing doctors about the symptoms - don't let anyone tell you different. I've been to the ER a lot, and visited several dr's and had test after test ran. After all those tests, it seems I'm in perfect health. The only thing they found was evidence of vestibular migraines, which isn't serious, and according to the MRI, had been going on for years. If the symptoms keep up and you still feel alarmed, don't hesitate to see another dr for answers.
Sounds like, for now, you have nothing to worry about if all of your current doctors have given you a clean bill of health. Keep the faith my friend.