My 6 year old son just told me he feels ugly

I asked him why but he didn't know what to say, I simply told him he's wrong and that he's the cutest kid I know (he is!) and he called me a liar.Children aren't supposed to worry about this stuff, could he be getting bullied at school? Maybe a different haircut or something would boost his confidence? I don't know how to proceed, this came out of nowhere. via /r/Parenting http://ift.tt/2awlHqE