what verses in the bible specifically mention that masturbation is a sin,?

It doesn't. Masturbation is not mentioned at all int the Bible.

My friend have u not pleasured yourself ever. My girlfriend of many years ago felt as long as she didn't use her fingers it was OK. I saw her using the corner of a table once. You should get some porn a quiet place and spend a day enjoying yourself

The Bible does not specifically mention masturbation—the deliberate self-stimulation that produces sexual arousal and orgasm. However, God’s Word commands Christians: “Deaden, therefore, your body members that are upon the earth as respects fornication, uncleanness, [and improper] sexual appetite.”—Colossians 3:5.

No such verse exists.

the one about Onan pulling his penis out prematurely and shedding his semen upon the ground.

http://imgur.com/gallery/e9DJjCo

None.

No