I have a phobia? im scaredd?

ok so alot i have this constant fear that someone is going to like be behind me or like idk i think of killers. no im not all screwed up trust me im not on drugs ever and never smoked. its just weird like when im home alone for example and i hear the tiniest noise, all these possibilities of what could go wrong pops into my head and i get so scared! also like in the shower when i wash my face then open my eyes i always fear ill open my eyes to someone standing there like just holding a knife or idk! ug i know i know its so weird but its scary and if theres a name for this id really eppreciate knowing what it is! thanks!! :)