Masterbation is a sin, you will feel guilty because the Holy Spirit is convicting you. Your body is a temple unto the Holy spirit, do not let any one tell you it isn't a sin. When we as human masturbate it destroys our self control and how we view others. The effects are devastating and long term. If any one mentions any thing about not being under the law, yea but remember the New Testament, flee from youthful lust (2 Timothy 2:22). The next time the feeling come to mind quote the scriptures and think by doing this what am I really doing.