How to stop being scared of everything? Life in general?

I am a worry wort. I worry about everything. I am a teenager. If my parents aren't home the minuet after they say they'd be, I freak out and start calling them frantically. When I have one symptom, like a headache or itchy skin, I think I have a terrible disease. My latest fear is the fear of murder/kidnapping/ and rape.Whenever someone looks at me on the street, I think they are going to track me down. I am really scared. I try to calm myself down, because if I think about it, why would someone kidnap me? and even if they wanted to, I don't walk alone or do anything that would put my self in danger. However I am really scared of someone breaking into my house at night and taking me from my room family. I lock all the doors and windows before I go to bed, but yet I can't seem to shake this fear. Also, I get a lot of Deja Vu, and I know this is common, but I can't help but think I am so worried about kidnapping because I "subconsciously" know its going to happen. Also, It is exam time at my school and I think I tend to worry about things like these verses my exams, right at time of my exams. Please, give me advice on how to calm myself down. Do you think I am going to be kidnapped? Please give me some advice.