I feel your pain and was in your exact situation. It's a very tough place to be in. Here's what worked for me.
Go out with your boys on the weekends. Settle in with your favorite "I'm getting fucked up tonite" drink. Mine is jack & coke. With your boys by your side and some liquid courage flowing thru your veins, be an asshole. If there are 3 girls hanging out drinking, jump into their conversation and say something to be a dick. In fact, say whatever you want to whatever girl you want, but be an asshole about it. The goal here is to get some great laughs and some good stories with your boys, not to go home with anyone. Do it right and you guys will have a hilariously awesome night.
Now, why would you want to do this? A few reasons. The biggest is that you need to build up confidence and fully embrace rejection. You need to not care what a girl thinks about you and that's a hell of a lot harder than it sounds. It makes them a lot more approachable too. Also, nice guys DO finish last. If you're a nice guy, if you meet a girl and she's nice, you might have a nice conversation and then she'll go home, without you. If she's not nice, she'll use you for all the free drinks you'll buy her and then go home with some douchebag. Chicks dig assholes because of their confidence. If a girl sees a guy who doesn't give two shits about her, her interest perks up. "If this guy seems like such hot shit, maybe he is real hot shit and I want in." Nate nailed it, how you present yourself is the whole key.
After a bit of this, you'll find that you have plenty of confidence to walk up to the hottest chick in the bar and say something to her like it's no big deal because it won't feel like a big deal. And she'll notice that. Ever notice why when you're dating, girls are always flirting with you and when you're single, you can't get a digit to save your life? It's because the taken guy's goal of the meetup is to chat, flirt, whatever, but not to bring her home and that's very apparent.
I suggest reading
www.tuckermax. com and the forums. He is a true asshole, but he can get a girl any time, any where. I highly recommend his "real advice" section, especially about how he picked up a girl at the checkout line. Masterful. While I wouldn't necessarily say "Be like him", read what he says and does, understand it and try to incorporate some of the confidence and bravado that he has. He even goes into depth about the how and whys it works.
This is a convo my friends and I have all the time, so I know it well. Especially since I was in your shoes and now am not single. It really is all about how you present yourself and your level of confidence. Getting that confidence is really, really hard to do, once you have that you're set.
There was also a TV reality show where Mystery and a couple other people who run a "game" training camp did. Corny as hell, but their shit really worked. They took the geekiest dudes, the ones who made it halfway thru college without ever kissing a girl, and toward the end the guys were walking up to girls and then walking out with them! They explain what to do, what not to do, and why. I can't remember what the hell the show was, but I'd highly recommend it.