I saw an interesting point raised by a girl in your situation. She said that instead of giving every girl the illusion that they're attractive, they should be taught that their self-worth should not be based on physical beauty.
Just because guys aren't approaching you, doesn't mean you're not attractive. Not that you being attractive should define you. It's been said that guys only approach average girls because they assume more attractive girls are already taken.
You get confidence by knowing who you are and loving them. You may not be a model or a genius but you've accomplished everything in your life thus far despite those facts. Accept who you are and what you look like.
You're not hideous it sounds like. Most guys are probably too intimidated by your looks. Or maybe you are giving of unfriendly vibes. I hate to use the 1-10 scale, but based on what you are saying, you are probably a 9--10 on that scale. most 9's and 10's often complain that they don't get approached wwhile women on the looks scale from 5-8 get approached more often and too often. Quite often guys, who lack confidence themselves, often take the easy out by approaching less attractive women because they aren't as intimidated.
My advice is to wear something warm and friendly. Get a good style, but not too over the top, you need to be approachable. If there's a guy you like, look at him and smile, or keep sending discreet glances his way. Also nothing is stopping you from saying "Hi, how are you?"
how old are you? because I've never had a girlfriend and I'm 23
I look myself in the eye and myself and I have a little heart to heart pep talk that goes something like this:
Listen up. Quit your bitching. You're not that bad looking. There're always going to be prettier girls and you're always going to feel awkward and you'll always be the klutz of your friends and people are always going to tell you you're ugly and gross. Buck up and get over it. Now put a smile on and fake your way through the day, fake that confidence so no one knows how depressed you feel about yourself and then, when the day's done, you can go home, put your pj's on, put some maple syrup on some ice cream, and sit by yourself with your computer and watch Netflix. But until then you get your ass out there and act like you deserve to be there with the rest of the population.
Whether or not I believe said pep talk is another matter. But it usually gets my blood boiling just enough to work :p