I get dizzy when I see/hear disturbing things?

I don't know why this happens, but sometimes when I see dark things (scary movies, read something scary on the internet, etc.) or when I see something really unnatural or weird (a strange Youtube video, a creepy song), I sort of freak out and feel like I'm going to faint. My face gets pale and I feel dizzy. Sometimes I even start shaking, or my stomach feels queasy and I don't want to eat anything for a while.

I can watch things like Game of Thrones or Supernatural and nothing happens to me. but when I see something else that really disturbs me I start feeling sick. Am I just faint-hearted? Could it be something anxiety related? I have been under a lot of stress the last two years (I just finished High School, 18 years old), and sometimes I got mini anxiety attacks when I felt overwhelmed by school. Why does this happen? What should I do?