Nadim, when you are sixteen your hormones are running riot. Always aim for the best you can to honor God, but please know that you are not condemned to hell when you slip.
The primary danger in masturbating, actually, has to do with the images you conjur up in your mind. These images can remain when you are married and make your wife, who will love you so much, seem less than the best. You don't want to do that to her!
Do the best you can now and know that if you have truly decided to follow Christ, He will do the best for you . And HIS best is pretty terrific!
Now, about that passage in Luke 12, the point is not to confess your SINS before men, but to confess Christ Himself before men. Some of the modern versions use the word 'acknowledge' instead of 'confess.' The idea in that passage is to not be ashamed of the Gospel or of Christ, but to live with Him in you every moment of your life.
And, by the way, when you ARE born again and Christ is within you, masturbating becomes rather nasty in your mind and you tend to shy away from it!
------------
Note, because I am a woman, I checked this response with my husband and he said that I had presented it correctly. But women can have similar problems -- and Christ handles all of it.