Guys are attracted to all different looks. Just because you think a girl is ugly does not mean a guy does. Sometimes what we consider pretty doesn't fit a guys standards. Many guys are not as in to makeup and fashionable clothes and are not in to those type of girls. If you are difficult to approach, just expecting guys to make the first move, well, again, a lot of guys would rather strike up a conversation with a girl who is easy to talk to and is comfortable around them than the pretty girl who won't even make eye contact with them.
It is a myth that "pretty" gets the guy. Another issue is not that you are not receiving interest from guys, but that the guys who are showing interest you have no interest in. There are men out there who are very bold, have no concept of you being out of their league (if that is the case) and will pursue attractive girls, but you may simply be aggravated that they are pursuing you. That is something that has happened to me. I finally realized I had to get over it. We cannot control who will pursue us, only who we show interest back to.