Masturbation isn't a sin but a 'necessary evil' in Islam. Islam recognizes the human need for sexual relief and thus masturbation is seen as a solution so that men won't commit adultery or rape etc.

Furthermore, you have lived a very sheltered life and should re-evaluate things to make your life and Islam fit together.

I'm Muslim too and read parts of the Holy Book and have decided what I would prioritize in my life based on the book and it's context.
Understand that Islam is (at least in my eyes) a personal religion, not one ruled by any institution.

As a result I decided to commit the sin of penetration before marriage.

Allah is merciful and while I won't know how He'll judge of me, I do know that honesty about your own wrongs is highly valued.