I remember myself at the age of 17 or earlier when I used to feel rather uncomfortable for being shy and reserved, especially with girls. But at my current age, approaching my 40th year I really consider myself lucky to have been shy, rather than extremely extrovert and unreasonably confident in my social approach, especially to girls.
Although being extremely shy may not give you the opportunity to train your social skills, approaching someone, attracting someones attention, gaining familiarity and comfort into social interaction etc.
Regarding girls you should find out later in life that not all girls possess the same qualities in their character. If you are extremely extrovert you may also result creating lots of extremely 'shallow' acquaintances which after all they don't offer anything positive, instead they become burdening in time, distracting to your personal lifestyle and harmful to your emotional integrity.
I personally admire shy youngsters as I realize from my own experience that they're more prone to virtue than the extremely extrovert ones.
I suggest in order to overcome your extreme shyness you find ways to socially interact more frequently, as doing group sports and excursions, learning symphonic music in an orchestra, learning chanting etc.
But beware, not all people share the same qualities and interacting with people of poor culture may really deteriorate your character and handicap your emotion.
Learn to carefully speak nonsense (the football stadium language) without using though filthy words, and try to look extrovert, but never make this a trait of your character.
Don't expect to find quality in socializing with people who don't possess it. Quality usually doesn't lie in excess; and this is true also for being social.