i have the same problem and the smell is from my anus
These steps may help u:
Make sure its from u .Thers a lot of people in the forums saying its from their anus and some people seem to think its from their nose.
Maybe ur mother cant smell it because u shes used to it.if ur in a smelly place for a long time u seem to forget the smell.
OR
maybe its because u are more tense and active in ur class or at social functins than at home.
I dont know if this helped.If u want to help me or anything
Please mail me at youcanhelp000@yahoo.com