Confidence comes with security,if you have 0 confidence then you must have lots of insecurities. Write down your insecurities, then divide them by what you can change and cant. If you cant change it then leave it to god. If it is something you can change then start dealing with them one by one. so for instance if you are skinny/fat,that is something you can change by going to the gym. If its your lack of knowledge,also can be fixed by reading maybe 2 books a week or so...etcetera Do them,starting from the easy ones amd work your way up and you will notice changes in the short future. Sincerely ThatDude