I have the exact same symptoms you are experiencing and let me tell no one can honestly tell what is going on. I find myself trying to diagnose the symptoms myself instead of my doctor because it aches so much. The pain is on my left arm and resonates from my elbow. I use the computer every day and have been since i was 10 years old. I am almost certain all the improper sitting positions and keyboard shortcuts graphic designers, such as myself, have to use have something to do with the everyday discomfort. It doesnt hurt at all it which is strange and during the mornings its feels at peace until i sit in the same position for too long or go to lunch and come back to my desk.
Coincidently, I just came back from getting a cortisone shot from my doctor. I was against it since day one but nothing has seemed to help. Oh and I forgot to mention. The first doctor I went to visit about my elbow had a MRI taken and diagnosed it as tendonitis. But Im left to wonder if its tendonitis howcome there is no pain! Im excited to hear anything you have found to help alleviate your discomfort.