Whyam i constantly thinking about death all of a sudden? some1 said subconscious dread of major change?

i think thats exactly what it is.. im going through a MAJOR change in my life in status life style financially my whole life is getting ready to change and as im getting closer im starting to think about death alot...i believe in GOD.. and very sensible person.. iim not thinking of doing anything to bring death or anything im just fearing it and thinking of all the possible things that are after.death. and i like why in the hell am i im only 18 can some please ellaborate on the major change thing i like 100% sure thats what it is. thank you