I find the only way to become more confident, is to over come the things that are causing the lack of confidence, aka your insecurities.
I had problems being confident, because i was self aware that i had bad teeth. I tried to overcome this by forgetting about it and not letting it get to me, but i couldnt. Even when most people never said anything (out of politeness mostly).
My body langauage was low, never looked up, had trouble making eye contact. I went a little further than most and had alot of dental work done (which was necessary, i wasnt just insecure for no reason)
The feeling inside was like none id ever had, because i was finally happy about how i looked, which most people will try and tell you isnt important (which it isnt in a perfect world, but this world is far from that)
My body langauage changed, i smiled, i looked people in the eye, i stood up straight.
It was great, mind i soon found something else to be self destructive about. I wonder if i will ever be truely perfectly confident.