I agree with the "people say" part. Friends won't usually tell you that you're ugly as sin...well, mine do, but they'd say that even if I was a supermodel, so they don't count. As much as I normally detest the "rate me" threads here, if you want an honest opinion, there's no better place than here. You've seen the way these people are - brutally honest is SOP around here. If you want to know how pretty you really are, I'd post a picture and ask 'em.
As to the approach, there are a lot of factors that'll affect it. What is your style? What is the usual style of the guys you approach? Sometimes, that alone causes the conflict. Example: if you're a rocker chick, you're probably not going to do well with a nerd who can name every past and present member of the X-Men, but thinks Eddie and Alex Van Halen are two guys who do Vegas shows with a tiger act.
Next, how do you approach them? How aggressive are you? Some guys don't mind a forward girl (this become truer as us guys get older), but most guys in your age range like to be the chaser. There's a big machismo thing going on for guys at your age. Huge. If a girl approaches a guy, the implication is that she's wearing the pants in the family and he may as well wear high heels and pearls. It sends guys into a panic.
Of course, they could just be taken/interested in another girl. Point is, there are a lot of variables and without knowing a little more about you or better yet, seeing you in action (which, obviously, we won't), it's hard to say for certain.