I am a large lady, most UK clothes shops don't sell my size. I used to be really shy when singing, always stood at the back of the choir or behind the PA speakers. I recently learned a couple of bold songs about fat ladies, (16 stone & Every Inch a Lady) and these usually go down very well which has vastly improved my personal confidence. So I think a lot of it is in your head. When you look around there are always people bigger and smaller than you - God made us all different it would be boring if we were all the same!