Is it normal that i am visualizing this?

I think I am really getting mentally sick these days. I am really frustrated and pressurized at the same time. Don't know what happens to me sometimes. I visualize of violence. Something is seriously wrong in me. I get suddenly sad with no reasons. I cry due to this sadness hovering around me. Due to this I try to suffocate myself. Sometimes I visualize of someone beating and physically abusing me and someone smothering me. After sometimes, I come to know that it was me only who was smothering myself. Sometimes I don't sleep till midnight fearing someone might attack me. But I think maybe I am hallucinating or visualizing or creating it in my mind only. Or maybe playing victimized. I haven't let my parents know about this. They notice my moody behavior but they think it's due to pressure. I do this almost everyday before going to sleep to get sleep. Even in middle of this visualizing, if my parents come I get aware of them and behave as normal to them. Till now it's not all a problem for me. But due to all this I  am losing all my concentration in day to day life. But I am afraid that in future something serious may happen to me if it is not corrected or treated. What should I do now?