I`ve been having lots of violent and messed up thoughts and dreams lately?

With the physical abuse and bullying you experienced when you were younger it is no doubt linked with how you are feeling now. Perhaps you subconsciously want to get back at everyone and show them that you are no one to be messed with. It takes a lot of self effort but you should first off stop looking at the pictures and stuff like what you linked. The chance of you killing someone luckily isn't that high but don't put yourself in a bad position and stay away from like kitchen knives and whatever (I used to feel like I could just pick up one and stab my mother..yeah I know I had problems too). Maybe ask if you can talk to a counselor at school or get an appointment with a therapist. They should be able to help you further from here.