"So let's skip right to sex then"
Really though it just comes down to understanding that not every girl is going to be interested to begin with. I'm a skinny guy, and some girls have commented on it. Most of them are usually fat so I don't care, but then there's some thicker curvy girls that say that too. I've actually had my back bruised by grinding on a girl with a fat ass while I was leaning against a railing. Nowadays I just figure these girls aren't my type, and don't even bother. Just find out which girls are interested, that you're interested in too, and work on them.
Though you can help yourself out with a few aesthetic changes. Choose a hair style that adds a little height, get a pair of shoes with a heel, hidden lift, or both, and then work on improving your posture. You could easily be 5'6" to 5'7" just from learning to stand up straighter. Also think about the way you hold your chin. Look at Putin in the picture I link. He holds his chin level with the ground, with a ramrod back. Compare that to the physically bigger biker, who ruins his posture by trying to lift his chin. You can see that he just ends up awkwardly jutting out his neck and having a slight hunchback.
http://cdn.theatlantic.com/static/infoc ... 133575.jpg