The first place to start is the gospel of Jesus Christ. He died for you. How special and loved do you already feel? On that alone, knowing how much God loves me that He had His only Son die for me on the cross makes me feel awesome. I feel best about myself when I look at myself through the eyes of God not the world.
Next thing: God put you here for a reason, that is to do His will for your life. It means He gave you special qualities and attributes that He has given no other soul on earth. With all these things you are to get to work doing His will, ultimately to glorify His Name and therefore bring your fellow brother or sister to Christ.
Get busy developing a relationship with the Lord and learning what He wants you to do with your life, this will put you in leaps and bounds ahead in the self confidence stakes and your battle against any self doubt from the enemy. God speed!