Is paranoia caused by misperceiving some happenings or by not perceiving some?
Neither. Unless you’re in imminent physical danger paranoia is caused by perceiving too much. In other words, you fantasize about all the horrible stuff that will happen to you and you believe it for the time. Learn to calm your mind and focus on your breath. Try some meditation techniques. Your mind is lying to you, it’s just a game, a make believe. Your body is fine, try and appreciate that simple fact. Breathe.