At a glance, I would say that not worrying about it would be better. Don't go looking for a relationship, but don't be afraid of one either. Also, being social is not merely a trait, it is also a skill. I'm an introvert, but I'm a LOT more outgoing than I was in high school because I've learned to be. It took me having more confidence in myself as a person to start relaxing around others. Regarding your first point (about feeling insecure of your body), find out exactly what it is about your body that you don't like, and find a way to improve it naturally, while also being prepared to accept yourself as you are. Using myself as an example, I've always had bad posture and I looked like a fat retard, but in the last year or so, I've learned a lot about correcting posture through exercise, and now it's greatly improved. I took the time to learn what I didn't like about myself, and how to change it. On the other hand, my hair is thinning (already) on my head, and, while that used to bother me, I've come to terms with it as there is nothing I'm willing to do to change it.
I see. Well I wouldn't ever recommend plastic surgery (it won't even yeild the desired results), so you must come to terms with it. But how you do that is not by merely accepting something that you think is negative, but by finding and fully embracing everything positive about you. Also, saying "i don't have anything to attract a guy" is unfair to yourself, as not every guy is that shallow. The kind of guy who is only attracted to a woman with giant knockers wouldn't appreciate you as a person anyway. Again, find your strength in life. If you're strong (in a figurative sense, at least), somebody will appreciate you for it.