Oh, little fish, trust us here… You may not want to be single but 13 is a bit young to expect much. It only SEEMS like everyone has someone they’re going out with.
I remember, all too well, being in your position at that age. I was short and stocky and awkward. It took a couple of years, but by the time that I was 18 or so things started to fall in to very flattering places. My lack of success with boys has done a 180.
One of the things that I would suggest would be to dress well. I actually have an example that I have in mind… This gorgeous specimen started dressing like this when he was 14. He didn’t look like anyone else and really managed to stand out in a positive way. He had an excellent body but had a very odd face shape (he’s grown in to it some by now). The other thing he managed to do was make friends with a lot of girls. This all has gone very well for him.
Next: Put down the video games and walk away from the television. Go learn to do some cool things that people will be just as interested in as you are. Go fly remote control helicopters, play guitar, learn to unicycle. Find entertaining things that work as a way to break the ice with the people around you.
One of the best things that I ever did for myself was to learn to draw. It’s one of those skills that keeps everyone around me entertained and comes in handy all the time.
In summary: Dress well, be a gentleman, and go find something unique to do. Don’t exile yourself, be friendly, smile often, and just wait until you’re older. It does get better.