Also, word to the wise - the longer you are without a stable/serious relationship and the longer you go on without bedding someone (especially at the very beginning) the more you tend to elevate the person at hand. More "feeling that special connection", more significance ("she's the one") and so on. Believe me, looking back at it ten years later, while you probably won't really laugh at yourself or anything and possibly you'll still feel something for that person in retrospect, you'll see how silly you were then.
+ you are unfortunately of the age when most girls are still... well.. unreliable and not solid for a good relationship. Well, guys aren't too, I'm not being sexist. But it's still all about searching one's true self, unbridled egotism, "testing" the other partner (from my experience women really do search for a stable anchor in the man and one of the easy ways to test it is... well, trying to play with him, really), it's all fickleness and fear of any kind of commitment (unfortunately that often lasts for a very long time with some people) and not being serious and "checking out the playfield".
My point is, keep holding on. I know it sucks, but you will get older and the people around you will start to behave more like... well, human beings. And it's great to have the opportunity to build something with the girl for the longest time, but you're still not late. Even if you won't start for another five years, that's still a lifetime ahead.
Just don't turn into either an incel or a "nice guy" (which is almost the same thing) or a douchebag or a jaded loser or an emo and you'll be fine, trust me. Good luck!