Please help im scared that i've seriously lost it!?

To start im only 13 and I've never heard like voices or any thing like that and dont say something stupid thats not gonna help at all.Alright so any time i see like any thing scary or anything dark i start to freak out my breathing gets fast and i feel like my heads going to explode! I start thinking about death and like what would happen if i died. now dont say just don't think about it i already tried that. But like the dark scares me too its like REALLY bad , like sometimes every thing makes me nervouse. have i totally lost it? please help!