We females are very complex. I find that sometimes my emotions betray me and things that I attribute to my husband are my imagination rather than reality. It sounds like maybe you are struggling with self esteem issues. We do not have to be stunningly gorgeous to attract the sexual desires of a man. On the other hand if you feel like you do not deserve it or inadequate, sometimes it is possible to transmit such vibes unconsciously. At age 20 I would not be too concerned yet. Just be open and interested in the men you meet. As women I think that we have an intense desire to feel love. Sex is wonderful, pleasurable, and an intense experience, but to have sex with someone with out loving him, for me is repulsive.