Hi, Tom:
I'm writing from "the other side". No, I'm not dead, I'm prolly older than your mom by a little. I've been through what you've been through before, more than once, so I can give you the benefit of my perspective.
You're 20 and you haven't had a romantic relationship.

Be careful what you wish for, you may get it. When you have your first big heartbreak (and you will at some point), you'll be wondering why you ever got involved in the first place. It's a double-edged sword.
When this girl told you that you had your standards set too high, what did she mean? You obviously have things that you feel are important in a woman. Don't lower your standards if you feel as strongly as you do. You may have won the battle but you will lose the war and you will be very

with yourself. It's apparent that she didn't measure up and though it hurts you, you're better off without her.
High school is a very cruel time in one's life. I was never part of the "in" crowd. Even in grade school several of the girls who thought they were truly something treated me terribly. I realize now, and you will also, that those people who try and make you feel bad about yourself have already hit their peak in life and are on their way down. They are extremely insecure and the only way they can feel good about themselves is to put down others. How incredibly sad is that? They are so hollow inside, and they realize it, but nothing good will ever fill that void.
You, my dear, are what is termed "a late bloomer". You haven't reached your full potential yet, at least where women are concerned. Everything happens in its own good time (call me a fatalist if you will) and it happens for a reason.
Not that the above paragraph makes you feel particularly good at this time and I'm sorry you're lonely. What kind of friends do you have? Do you have both male and female friends? If you only have a few female friends, friends that you pal around with and your friendship transcends the gender difference (like a sister, if you will), I suggest you find more of them. Take up a new hobby, join an organization, volunteer some time, whatever. Meet new people.
It always helps when you join a particular group because you'll have something in common and that will serve as a springboard to other things. It kind of takes away some of that awkwardness in the early phases of a relationship. Any kind of relationship must have friendship as a basis otherwise it will not last. Romance comes with time--kinda creeps up on you.
That doesn't preclude your falling madly in love with someone and they with you. However, you still need a strong foundation. The first few months are full of sonnets and symphonies but eventually the orchestra folds up and you get around to the business of dealing with day-to-day stuff. You both stop "making nice" and revert to being yourselves. That's when the real learning comes in and can really test the strength of two people's feelings for each other. If it fizzles out then it wasn't meant to be. Live and learn. If it can stand some of the strains that naturally occur with any friendship, chances are pretty good that it will last.
At 20 you're just starting out on your Big Adventure. Just because you don't have a girlfriend now doesn't mean that you will be unattached for the rest of your life.
I had decided from a fairly early age that I wasn't going to get married. Then I met someone when I was in college that knocked me off dead center. However, it wasn't meant to be (and I'm eternally grateful for that) and I learned several lessons. My relationships were few and far between--I'm talking years. When a relationship ended it took me a long time to try again. I was very fortunate to have a support network of both guys and women. My male friends were very much like brothers and made me feel important. We never liked each other except as friends, and we would keep each other true. IOW, if they were doing something that was a bad idea I could tell them so and vice versa. We weren't afraid to keep each other straightened up and flying right.
I didn't meet the man I ended up marrying until I was in my 30s and we were together just over five years before we married. Neither of us was ever planning on marrying, it just happened.
OK, so you don't have a girlfriend right now. If you have the chance, do something you've always wanted to do. Chances are that you may never get to do it when you get older and you may end up regretting it. I did lots of things when I was between relationships that I'm glad I did. I moved to an apartment that was in a place I wanted to live, I traveled a great deal (by myself), I ended up getting a Masters Degree. They may not seem like great things but I did them and that's all that mattered.
Be friends with yourself. Get comfortable in your own skin. If you don't like yourself, how can you like anyone else? Also, don't just look for the "first row" girls (the analogy is bleachers in a gym). There are others a little higher up that have a great deal to offer but are too shy to approach you. They may not have the looks the front row girls do (and I'm not saying that all you care about in a woman is how she looks) but they have an inner beauty that the front row girls will never have.
I can see I'm starting to ramble so I'll close. Good luck and do keep posting.