What can I do to be more...wanted or desirable?

People tell me I'm pretty.I don't think I'm ugly.But iv never had a bf before.I'm really shy at first but I'm really outgoing when you get to kno me.I don't know why I'm still single tho.Iv never asked a guy out before because I'm a lil afraid of rejection.So how I can I be more "wanted" by guys without being a slut?