A lot of guys wear make up on a night out at expensive, exclusive places in the States.
She cheated on a 15 year old version of you. Girls cheat on even the best sorta males out there. Thinking of media examples, even Justin Timberlake and Ben Affleck were cheated on for petes sake. Will Smith's movie hitch was actually inspired by a cheating ex. A simple google search shows me that Will Smith said this:
"My first girlfriend cheated on me when I was 15 years old, and I processed in my mind that she cheated on me because I was not good enough. And I remember my walk home after I found out, and I remember just vowing to myself that I would never not be good enough again."
And if the guys say anything, then be like 'It feels to weird to imagine myself without it, it's there on me now I don't mind it.'
So in this very context, you need to get over yourself and stop thinking you're less of a male and have nothing to offer. Maybe you went from a nut-loose girl anyway..
You just got to focus on loving yourself and having less inhibitions, going out there and doing things for you and not for anyone else. Then you'll find that you'll transcend the levels of what your ex-girl usually goes for in terms of character. You're not doing this for revenge, you're doing this for you. You'll find that your personality is developing a lot as you join societies, meet different people, focus on individual time and doing things you love and really devoting a lot of time for that. Personality is a by-product. You don't have to offer anything to anyone. Just don't hide yourself from others, it'll allow certain people to connect with you and can thus appreciate your visions in life because you showed them what you're about.
My advice is to find a girl that would accept you for yourself being 3/10, because when you get ready to go out, she'd be getting more than what she wanted looks wise. It's kinda like clark kent by day, superman by night I guess? If it's a simple concealer and eye lash curl, it's not as if that's going to take very long to do anyway, it's kinda like putting gel on. If you were to MAKE YOURSELF look like a GIRL, then I think it's a bit weird.
Work on things like your body. Get yourself the perfect body and your face would look even nicer because it will get more muscled/chisselled. Working out is one thing that launches a males looks. So basically, if you're a 3/10 now, if you worked out then it'll most likely be upgraded to a 6/10, providing you wear nice clothes, have a good style about you.
Remember that people may have opinions and thoughts and make negative comments, but people talk all sorts of rubbish, you may as well pick and choose what ones to listen to. STOP making things define who you are. Happiness is from within. Accept who you are and love it.