Why am I bloodthirsty? Has anyone else ever felt like this?

please don't judge me,though i know this is weird. I'm a very non-confrontational person and im not outwardly violent at all,but i have this huge urge to be. im in high school and i notice that when i see my clmates-friend or otherwise-i start to twitch. if i see exposed skin and veins-especially inside the elbow-i go nuts inside my head. all i can think of is biting them till i rip it out. i actually crave the blood. and when i walk alone through the halls and see other people my hands will tense and crimp like claws. i dont get it. it doesnt scare me and ive dealt with this for a long time so i dont believe to be a threat,but im asking if anyone else feels like this or know why i am.