Quentin's Virginity Issues

What drives Quentin's obsession with the virginity of himself and Caddy? His thoughts always wind back to something related to Caddy's promiscuity or marriage. Father tells him that the only reason Quentin is upset with Caddy's pregnancy is that Quentin himself is still a virgin. Father then explains that virginity is just a concept invented by men. How does this affect Quentin's view of the meaning and idea behind the word "virginity?"