Triggers of Shingles ( zoster)?

I got shingles about 3 years ago in my senior year of high school. It was a horrible experience and I am now feeling the same pre-symptoms as I did the first time. I am pretty stressed because of school, but I don't think that's all that triggered the reaction. I recently was made to take the varicella vaccine for a second time and I'm wondering if that could have been the trigger to start up the virus again? I would appreciate greatly if someone knows the answer to this, I haven't been able to find any.