people feel confident when they are able to excel in a certain
area of field.
be it someone who is handsome, pretty, good at a particular sport,
good at presenting himself/herself, bla bla bla.
so as long as you are good at something, the confidence would be
there.
what i would suggest for u is to get a "fashionable" haircut, build
up on your body and your facial complexion. by achieving this, you
feel good because you look good. when u feel good, it'll give you
an advantage when it comes to communicating with others. who
wouldn't want a "shuai ge" to talk to them? 
alternatively, go pick up a sport and excel in it. you'll notice
that many sportsmen have got an "aura" around them. the aura comes
from being confident and believing in themselves. believing that
they can perform for others to see.
some people might say that talk is cheap. when it actually comes to
doing the real thing, it is much more difficult.
however you only have one life. it's really up to you to live the
best you can.
Good luck in your quest for confidence 
