You know something funny? People
think that guys go for pretty girls and that's what matters, but that isn't really how it works in real life. When I look around myself, then it seems to be more like vice versa sometimes really: it's the girls that don't shine out with gorgeous looks that have boyfriends, while the truly beautiful ones remain single. There's many other qualities that are
much more important than looks. And if you think about it... if how pretty a girl is makes all the difference to a guy... is that the kind of a guy you'd want to be with anyway?
Another thing to remember is, not having a boyfriend at 13 really isn't the end of the world. I'm 17 and I'd dare to say more than half the girls I know don't have one... and for most of them, it's not something they see as a problem! Despite what the media wants you to think, your life isn't defined by whether you have a boyfriend or not. Being in a relationship isn't the great universal key to happiness. Staying true to yourself and doing things that truly matter to you and having fun with that would probably come a lot closer.
About attractiveness actually... for one thing, different people consider different things to be attractive. What is even more important is that what people see as attractive is very often not even actual looks at all. It's the way
you see yourself, how confident you are in yourself, how friendly and helpful you are towards others, how easy-going you are maybe... I know totally average-looking girls that are insanely popular with guys... people in general really...
Oh, and, by the way, are you
sure about not being gorgeous? I won't go saying that you definitely
are, because I haven't seen you so I wouldn't know... but I know that, for example with myself, I consider my appearance rather plain myself with a bunch of things that could be improved... oddly enough I've had quite a number of people tell me they consider me very attractive, sometimes completely out of the blue... I still don't know what to make of that, hehe

What I mean is, that, just because you don't consider yourself beautiful or maybe some nasty person has told you something bad about that in the past, doesn't mean that's how everyone sees you.
Okay, wow, this reply's gotten pretty long... I better finish up

Don't worry, if you just feel good about yourself and what you do, you can have some real fun... and that will be far more likely to attract the nice kind of guys than anything you might try to make yourself to be that you think might make them like you...