How Many Hail Mary's?

I was kinda hesitant, writing about sex so early on in my blog, but I'm throwing caution to the wind because it's what's been on my mind.  I've been thinking about a comment someone made for a while now so I figured why not blog about it!
Ok so, one of my asshole friends that we'll call Tracey was talking to this weirdly religious dude, we'll call him Jesus Jawn or JJ for short.  So JJ had all these rules & regulations about premarital sex and blah blah blah mean while back on the ranch dude has a whole kid that he conceived out of "wedlock" (do people still use that term in the 21st century?). Moving on, what got me to thinking were his thoughts on masturbation.  Tracey told me that this guy JJ won't even masturbate because he say's it's a sin. Word!  Masturbating is a sin?  Now, there are many things about Christianity that confuse me and this is one of those things.  Being a single woman, this just so happens to be a part of my life; shit even when I wasn't single it never hurt to work it out solo from time to time.
So here's my gripe, I know I don't live a perfect sin free life (like all of you) but I do consider myself a Christian & I know sex before marriage is wrong but why would masturbating be considered a sin?  My list of sinful activities is long enough without having to add this to it.  I can understand it being frowned upon maybe but not a flat out sin.
The purpose of having sex, from a religious standpoint, is to procreate and that's the reason behind the no premarital sex thing but what's the rational behind the no maturating rule?  What if you're doing it in place of having sex with someone you aren't married to?  Shouldn't you be rewarded for opting for the lesser of two "evils?"  I'd need to see it written, someone please educate me on exactly where it says solo sex is a sin-- I'm talking book, chapter & verse.  And since Christianity  parallels with so many other religions I'm curious to know if any other holy book outlines the do's and don'ts of self pleasuring.  Am I alone when I say the best orgasms I've had I've given to myself?  How could something so great ever be wrong (ok, I know plenty of things that feel good aren't right but just go with it)?  I don't want anyone getting the wrong ideas like this is how I spend all of my free time but we're all adults here-- it's something we all do (everyone except for JJ).  And as I've been taught, a sin is sin none greater or lesser-- so would I have to pray as hard a the guy that just murdered someone just because I was bored on a Saturday night?