Hey man, I'm 17 too and used to be like this. All through middle school I never got girls and would be made fun of for it. I know, this sounds ridiculous, but it was just the situation I was in. So when I was a freshman, I made it my mission to kiss a girl. While I fluctuated in my determination throughout the school year, one night I was been invited to a party and knew in my heart that THAT was my chance.

Here's a step-by-step guide on how to do this:

1. Pick a Friday/Saturday where you know there will be a party. As you've said, you have friends that are good with girls. Parties are only occasional in most circles, but if your mates are cool, they can probably find one within a month.
2. Do shit the day of. Go on a 5k. Go to an art festival. Go see a great movie. Ride a bike. Just do shit that will make you feel good about yourself.
3. Okay, so now it's like 5 or 6 PM. Take a loooong shower and really clean yourself. Wash your hair twice. Pretty much don't leave until you feel like Mr fucking clean. Brush your teeth. Put on deodorant. Style your hair. Hell, if you have pimples put on some foundation. Anything and everything to make you feel great about yourself. You can even put on as much cologne as you'd like, if it smells good.
4. Now meet up with your friends. The BEST thing you can do is force yourself to be very vocal as soon as you get with them. Otherwise, you may not be as confident. Call shotgun, take the aux cord and play your favorite song. Open the window, smoke a cigarette. It's your night.
5. This part is crucial. Go buy a red bull/monster/whatever before the party. The caffeine will boost your confidence, happiness, and alertness levels.
6. Go to the party. If it's small, just have fun. You don't have to vie for a girl's attention. Talk, hang out, and if one girl notices you talk to her, listen, and take her hints! If the party is big, then throw your old self out of the equation. Have as much fun as possible. If you can't dance, dance. If you don't smoke, smoke. If you don't know that person, talk to that person! You can be the life of the party if you have a ton of fun. (Drinking is optional)
7. Near the end of the party, the amount of careless fun you should be having must have spread. Girls will be drawn to you not for looks, confidence, or whatever bullshit. They just know they'll have a good time around you!
8. This is the part that's big: break off from the party with one of your mates and 2-3 girls. This should happen naturally, say, with the girls you've been talking to consistently throughout the night or the ones you most vibe with. Go to a cool, chill spot. Maybe a campfire, or a separate room. If you know the host, ask before venturing where you shouldn't. Make sure it's not somewhere people can come In and interrupt.
9. Once in there (and this much easier while trashed) talk with the one you like/one that seems interested, one on one. Be her friend, be funny (not manipulative). If her friends and your friend pick up these signals, they should know to discretely leave. They eventually will.
10. Once they do, wait a moment, and if you have something to say, say it. Then lean in and suck face. It's that god damn simple.

I pretty much did this same thing three times and never had problems with girls again. What I learned is that you just need to radiate good energy by having fun and feeling good about yourself. The power is within you!

Tl;dr Have fun, be fun, seem like fun to be around and you'll get the girl. Getting drunk as fuck is optional.