Why cant I watch scary movies?

OK I have not been able to watch any kind of scary movie through out my life its not really the scary part that bothers me but its the gore in movies i mean i really want to be able to watch any movie i want to watch. Ever since i was young I have not been able to i don't know if it was something that happened in my younger years but I don't think it was anything like that. I really want to be able to watch gory movies I mean zombie movies like zombie land and stuff like that. I am 18 does anyone know how i can fix this?