Asking people if you smell

My parents don't believe I smell- for some reason they seem immune to it even though I've suffered for this condition for seven years (maybe they've grown desensitized to the smell)? I just confronted my dad about it after he said again it was just something I was making up. (strange how he picked today to say this as just today when I was walking home a total stranger yelled that I smelled like shit). Anyway, he says he won't believe me until I get someone to write a letter saying I smell bad. I've been considering asking a teacher of mine if they smell me. How bad of an idea do you guys think this is? Have any of you guys tried doing something similar? ANY AND ALL ADVICE IS WELCOME!