I have severe bdd and I haven't left my apartment in 4 months.
Why do you feel that way?
I have a scar on my leg and a huge, ugly visible vein.
You don't need to feel ashamed for having a big ugly scar. Talk to a counselor, who can help you navigate your feeling about what people will think of you.
I don't think that I'm supposed to be a person.
There's no one who's "supposed" or not "supposed" to be human; we're all just born human because we're the progeny of humans. Everyone has flaws. With help, you can learn to accept your body and focus on what you like about yourself.