[[[[[[[[[[[HELP]]]]]]]]]]]]]]]… I'm terrified to answer my door!!!?

Whenever someone knocks on my door, I run and hide. I don't know why I hide, because it's not like they're gonna come in and try to find me, but I just hide. I hate when I order stuff off the internet because UPS comes knocking at my door and sometimes I get so scared I don't answer hoping they'll leave the package on the porch. Pretty muchh when anyone knocks on the door I run. It could even be my family. My mom sometimes has to call and say "It's me at the door" in order for me to open it. There's nothing that I know of in my childhood that could have caused this. I wasn't molested, physically abused or neglected. What's wrong with me :(