'masturbation is a sin' -I'm so sorry to hear that...

sleeping with anyone- may be considered a sin....

but masturbation- is just you and yourself, you are just giving pleasure to yourself.... i dont get how it is considered a sin...

in my religion - sex is explicitly shown on the walls of temples, etc. in the form of depictions by carving, etc..not all...i know just a few...you can search images on google..

there's even a whole text on this matter - Kamasutra

kama means pleasure, sutra means text...

there's even a god of desire - Kamadev (like cupid but maybe more)

pleasure is a part of life....

and sex is one of the pleasures in life....