Nilor, dear. Social skills, dating skills, are just like any other skills. The good news is; at your age it is a matter of mere weeks, maybe months to aquire those skills.
Your post reminded me of myself. I was a loner for much of my childhood. I had a few unpleasant experiences with kids, balanced by too few pleasant experiences. Kids can be cruel, and some people stay kids until high-school graduation. I told myself: “Okay, if this is how people are, I prefer the company of a few trusted friends, my pets, and my books and my ideas. Going out in public is a chore, and I will avoid it as much as possible”.
Understandably, but onfortunately, I developed the attitude to go with it. I told myself I WAS a loner, by choice and by nature. I told myself most people were “the other”. “They” were different, and sometimes, I felt, way “better” then me or far, far below me. (of course, nature geeksm and gothics, etc, were my kind too, but normal people? No.) It was kind of an interesting, dramatic problem to have, being an “other” in a world of “normals”. 
Of course, the problem was much smaller, and much more mundane and ordinarily human. I just had had too little guidance in aquiring social skills when I was a kid. I had been left to myself too much. The result was a kid that WAS a little weird, sometimes arrogant and bitchy, and sometimes too insecure. I was a good person, but my awkwardness may have made me unpleasant at times. To top it all, I did not invite others to approach me, nor did I approach others.
My opinions were intelligent and original, but, I just had trouble communicating them well. (unlike you, I must say, your OP is very well written!).
So, during childhood and aolescence, I was in a vicious circle of withdrawing - little social succes - making up reasons why I should withdraw “they won’t understand me anyway, I’ve got nothing to expect from them”, etc.
If you recognize anything in me, here’s what I did about it.
I read books on social skills and manners. Not self-help books, because there wasn’t anything fundamentally wrong with inner me, as there is nothing fundamentally wrong with you (take my word for it, Nilor, you are just as ordinaty as I am ) Instead I ordered books about manners, because manners and social graces was all I lacked in, and improving my manners were my key to getting more succesful social encounters. I recommend the author Judith Martin (Miss Manners) for her wit, and her insight in how people and social situations *really * are. Just try, for instance, her books " the right thing to say" or “The guide to raising perfect children” or 'The guide to excruciatingly good behavior"
Could you perhaps, for a flying start, ask a female friend of yours (or a female shopattendant) to to clothes shopping with you? She could also take you to a hairdresser, to get a contemporary, fashionable look, even if it may not be entirely “you”. Think of your manners and your appearance as your window shop. Your product (the inner you) is a good one, and all that is required of you is to make it less hard for other people to reach you. Your customers will pay you abd themselves by lessening each others loneliness (as you have done by posting your OP and I by posting to it) and showing you and themselves, that companionship is a nice alternative, at times, to books, hobbies, pets, nature and a few trusted friends.
Good luck.
