Baptism doesn't save you, only God/Jesus/The Spirit does that.  Baptism is an open declaration of your love and submission to God.  If you want to reaffirm your statement to your church and friends, they will always let you do so, and if you want to be rebaptised, talk to your pastor to see if he is comfortable with doing so.  I can't see why he wouldn't, and if it will help give you peace, I say go ahead, but please know, if you have given your life to God, you are saved, and baptism is only to show others of your promise to God.