I have a creepy fascination with death, its turning bad?

i am a 15 (almost 16) year old girl and i have a very strong fascination with death, i used to be extremely suicidal, but have toned it down. however since then i have been having dreams and fantasies about death, i love anything and everything that has to deal with death! it did not bother me till my mother started to call me morbid because of things i would say. and wen i was joking around with my friends about different threats mine was " im going to skin you alive,gut you hang you by your intestine, throw u in a boiling pit of acid and watch u burn, then play slip in slide in your blood." i was kidding of course!!!! but the fact that it came out so easy and seemed well thought out scared me. not to mention when i meet someone i can picture a way to kill them in my head...i would never ever harm someone its beyond my nature im to kind and loving but these things scare me deeply. i often blame my past, for i grew up in a very bad environment, but i just dont know anymore, i feel so....insain.