Not to sound cold or uncaring or anything... but keep trying.
It takes time, its not something that you try once and miraculously get a gf out of. Plenty of people, non-aspies included, don't have gfs by 20 and later.
Keep trying... school is a good option, even if there are few girls in your major (but regardless of major, if you're school has other majors, may be girls there too).
Later on you'll have a job which you may find girls there too... keep checking out online sites looking for people are are AROUND your area, don't limit to them just within your city/town... if there has to be a little drive.... its worth it if its someone you like, no? And even if it turns out to fail because of the long distance, you can gain experience and confidence from it, and that may reflect positively for trying around here. Supposedly girls can notice if a guy is confident or not, and if you're constantly feeling insignificant for never having had a gf, least after that you will have one so can feel a bit better about yourself.
I don't know what NGOs are, but there are still clubs and meetups and other things around you may be able to find... librarys and stuff as well, if you happen to see a girl in you're favorite book section you could recommend some books to her and stuff (just don't be too creepy... its rare to happen, but you never know, might end up sitting down for coffee and getting together again).
There are plenty of avenues, and it seems that a lot of it happens w/o one actively looking... someone in an everyday place, rather than a bar.
And while yes, bars may NOT work for you... you won't know until you give it a try... but if you get easily discouraged and hurt from nothing working then don't... but if you think you can control those emotions, try, you never know... there are actually girls out there who do not like the cocky "stud muffins" and prefer real people.
But you just have to make sure you don't seem desperate... maybe you'll have to become friends first... it varies upon the person, but desperation isn't a good thing, generally makes the girl feel creeped out.
But again, you are only 20. Keep trying those many methods, it doesn't happen simply because you decided now you want a gf, and you'll try this and they'll come... it is something that comes with time, and the more open you are to chances, and more you try (--- again, not desperately ---) more likely it will happen.
Another thing to think about... why do you want a gf? The answer varies amongst different people, and girls are generally interested for completely different reasons... but it helps to evaluate exactly what you want out of it.
As a girl, when I see ppl wanting a gf for reasons such as "to get laid," "to fit in," "because its something to do," "because everyone else is," or "because its fun." I get discouraged... if it was "because I want to find someone I like"/"for the future"/"for companionship"/"someone who means a lot to me"/"because I want to share my time with them" and stuff, its much more oriented on WHO your gf is, rather than merely having a gf... that is a lot easier for me (note: "me," not other girls, there are plenty out there for the same exact reasons... but feels so shallow to me) to handle.... usually those reasons come later on, and in early 20s, the reasons tend to be the former... but its still something to consider
If you're reasons are the former, then you may try appealing to partying girls and stuff... try to find parties and bars and stuff to find girls... but if its the later, then you should look more in your area of interests, school, everyday ppl who aren't actively searching for a guy, because they don't wish to be a trophy, but rather be valued for who they are.
Just some things to think about, you don't have to agree with the last stuff, its from a particular girl's pov after all (me), but the first half hopefully should help you.
Just hang in there, things change with time, but don't give up and become pessimistic about it, nothing will come from that. (Now, you may stop actively searching for someone and still find someone, but if you say... go "noone likes, me, forget this, I hate girls anyways" then no, nothing will come from it.)
Good luck!