"I barely had any communication skills, absolutely zero sexual experience (haven't even walked holding hands with a female - even today) and the reputation of being a geek. And you know what? I realized I wasn't a happy person anymore."
It might prove almost impossible to fix. OK I'm talking from about a bit different perspective because for me programming (when I was young) an only occasional hobby and I was rather the "otaku" type of nerd, I spent most of my time with swords & sorcery -style books, games, etc. So it might be different, but:
I tried to fix it at around 17. I wanted a girlfriend. I focused on the superficial parts of it: went to a gym, got some muscles, boughts some designer clothes, went to clubs (alone), got piss drunk and tried to pick up girls. And convinced myself this is how normal, extroverted people do. Of course, with one difference: they don't go to places alone. I did - I didn't have friends and when I had something like friends I didn't like it, to go with them to places, it felt it limits my freedom, it was just so convenient to go alone. So what I did was actually I tried to copy the superficial parts of extrovertedness such as the fancy clothes, without the substance of it (actually making and keeping friends, or generally, enjoying the company of others including things like "chatting", "just dropping in to say hello", and so on). I think I must have been unusual - someone who looks like a typical extra-cool disco gigolo (I think in the States it's called "guido"), but a typical shy introverted guy nevertheless who keeps looking at his shoe and likes to be alone.
Guess what, it didn't work. I tried it for 7 years, until about 25, had very little success, 3-4 relationships each lasting about 3 weeks. That's not too much, I guess.
Now at 30 I became something sort of a philosophy geek, I'm more introverted than ever, because after reading up a lot of philosophy, history, economics etc. I just can't talk with most people at all, simply because they are not interested in anything I would like to talk about, and I am not interested in what they want to talk about (they usually want to talk about other people, which is the least interesting subject to me).
If I could start over, if I was again at 17, with a still fairly open and malleable mind, when I was not yet too deep and detached to be unable to talk with people and make friends, I would take care not to become too knowledgeable, not to read too much, don't go too deep into philosophy etc. and instead of all those superficial approaches to extrovertedness (gym, designer clothes, clubs) I'd probably try to become more sociable, try to learn to chat and to like to chat.
(But you can't start over, of course. By 30 some parts of the mind just get rigider every year and you just keep doing what you did before. Habits, you know. )