It may have been caused by the mercury fillings. But don't rule out other stressors as contributors.
For a lot of us...it takes a while to understand what a "stressor" is and what types of activities it includes. Because of this, we continue to do things that we we don't cosider to be stress, but they are.
Did you do any of the following to extreme?
Heavy weightlifting or other agressive exercise.
Watch a lot of p 0 r nogrpahy or spank the monkey excessively
Play a lot of aggressive video games for hours where people are shooting at you.