Most Helpful Girl
Maybe it's not your height, lankiness, or looks holding you back, but actually your insecurities that are tied to your inexperience and your looks?
Gain some confidence. Maybe try to work out and gain some muscle -- not necessarily to look better, but to literally feel better since exercise tends to have that awesome effect. Learn to love yourself and be more friendly. People are probably intimidated by your height, so show them that you're a nice/cool/chill person.
You're definitely not the only 20/21-year-old to have never had a girlfriend before. You actually have a pretty good excuse considering you were in an all-boys school growing up. If it makes ya feel any better, I had my first relationship ever at 20.
There's nothing wrong with your height, by the way. You're tall, thin... now you just gotta dress real nice and maybe you'll have a model-vibe going on =) good luck with everything.
Most Helpful Guy
6'4" is much better than being 5'4.5".
Just learn to accept it and be confident.