This is something i can relate to in a big way. For me, the two things that helped are Bodybuilding and Boxing. While both have been mentioned here already, i honestly can't overstate how good both of them are in building up your self esteem and belief in yourself.
Bodybuilding is amazing because you literally get to watch this visible transformation happening in front of your eyes. You see the weight climb, you feel parts of your body grow and strengthen, you feel better and better each day. It's an amazing thing.
Boxing too works wonders because it really teaches you to rely on yourself and to think on the fly. You learn to think fast, adapt, rely on your training and to always be looking for an opening. It works wonders on your mental state and physical fitness (just be careful which gym's you go to).
TL;DR, do both, or any of the number of awesome choices people have recommended like BJJ, or any other competitive sport. You'll notice the change and thank yourself for it.
Bodybuilding is amazing because you literally get to watch this visible transformation happening in front of your eyes. You see the weight climb, you feel parts of your body grow and strengthen, you feel better and better each day. It's an amazing thing.
Boxing too works wonders because it really teaches you to rely on yourself and to think on the fly. You learn to think fast, adapt, rely on your training and to always be looking for an opening. It works wonders on your mental state and physical fitness (just be careful which gym's you go to).
TL;DR, do both, or any of the number of awesome choices people have recommended like BJJ, or any other competitive sport. You'll notice the change and thank yourself for it.